How to Make a Rainwater Tank from Recycled Plastic Drums

recycled plastic drum water tanks
My rainwater tank array made from recycled plastic drums, 1300 litres capacity

Rainwater is a valuable resource that is largely under-utilised in urban environments. It’s one of nature’s free resources that we can use to grow food, and considering that Australia is the world’s driest continent, rainwater is a very valuable resource, far to valuable to let it run down the drain!

Why Small Rainwater Tanks Are Worth the Effort

You’ll hear many opinions about what size rainwater tanks are worthwhile and that “anything under whatever size is not worth the effort”, and so on.

Most of this rhetoric is based on the assumption that people have a nice big house (which they own!), with a perfect roof, plenty of free space in the back yard to put in some really big tanks and finally, money to pay for it all.

Let me say, if you’re growing a garden, you’ll need all the water you can get, and every little bit makes a difference. If you can get it for free, it beats paying for it. With water restrictions in Australia, rainwater collection can really make the difference for a garden surviving through a hot summer.

Ultimately, we can choose to utilise the resources that nature provides us for free, as limited as they may be, or we can simply let perfectly good pure rainwater run off into the storm water drain… The choice is ours.

From experience, there is a place for small capacity water tanks in urban environments. Small capacity water tanks work in places such as rental properties, small courtyard gardens, and even big back yards on a budget.

In these situations, the considerations for choosing a water tank are completely different to the big house/big budget scenario.

In a rental property, you may want water tanks that are small enough to transport from place to place, can be dismantled, and can even possibly fit in a regular car for transportation (or a bike trailer for that matter!).

In a small house or unit, the water tanks must be able to fit through any doorways, gates and access paths to reach their final destination in the backyard. Additionally there is only limited space in most small backyards or courtyards anyway.

If you’re on a budget, the main criterion is cost. Just because a person doesn’t have loads of money doesn’t mean they can’t do their part in living sustainably!

What is the Most Cost Effective Number of Plastic Barrels to Use

You can purchase small tanks and install them yourself, or you can make them yourself out of recycled materials. Cost is the deciding factor here. Even when using recycled materials, the tank fittings usually must brought new, and they can quickly add up cost-wise.

A good friend of mine, David is a water-expert, and has done extensive research and costing on setting up small tanks to harvest rainwater, and he has come up with some significant findings. In his own words:

After working on the possibilities I came to the conclusion that going beyond 3 barrels was not really economical. I feel there are better commercial options – or look into buying something second-hand. Five barrels interlocked with stands, overflow and a tap is going to cost approx. $300 in materials. You can buy 1 kilolitre tanks for $200 or less.”

He is suggesting that a setup utilising three barrels is the biggest you would go in terms of cost effectiveness.

David has come up with some great designs for constructing rainwater tanks from interconnected plastic barrels, and with his permission, I’ll present some of the designs in the future.

For now, I’ll share my own designs of the setup with the blue drums pictured in this article.

How to Build a Modular Rain Water Tank System

Here are the step-by-step instructions for building a modular water tank system which works either as a single tank or as multiple tanks connected together for greater water storage capacity.

It’s all constructed out of a recycled plastic drum and a handful of common irrigation fittings that you can get from most hardware of garden outlets.

First, here’s the basic design:

diagram DIY home made rainwater tank
DIY rainwater tank diagram

The following instructions are comprised of three parts:

  1. The construction of a single tank setup
  2. Additional steps required for the construction of a multiple tank setup
  3. Connecting to a pump and further enhancements

Step 1 – Prepare the Plastic Drum

Obtain a plastic drum with a lid for use as a water tank. Clean and rinse it out if necessary.

The plastic drum used in these instructions has a capacity of 220 litres (55 gallons). The lid is not shown in picture below, as it was left off to air-dry after washing it.

recycled plastic drum for rainwater collection
Recycled plastic drum with 220 litre (55 gallon) capacity

Step 2 – Gather the Tank Fittings

Some tank fittings are required to construct a rainwater tank. In this section we will list all the parts needed, and explained what they do.

For a basic single tanks design, you will need:

1.   20mm Threaded Tank Outlet (Bulkhead Fitting)

These are used to attach connections to the tank. You will need two of these, one for the outlet tap at the bottom of the tank, and another for overflow pipe at the top of the tank if you choose to use one.

20mm threaded tank inlet bulkhead fitting
The threaded tank outlet has rubber washers on either side of the tank wall, the one inside the tank is the most important!

2.   Brass Tap or Ball Valve

For the tank outlet where the water comes out of, any type of tap can be fitted to turn the flow of water on and off. Either a common brass garden taps or a 1/4 turn lever handled tap (ball valve) are good choices.

When buying a tap, select one with the correct sized threaded outlet (where the water comes out, and a hose connects), as they come in two sizes, a 3/4″ outlet and 1” outlet.

The standard brass garden tap size in all states in Australia is a 3/4″ outlet, except in NSW, which uses a 1″ outlet tap.

Brass taps can be purchased from hardware stores and plumbing supplies stores

The threads at the back of the tap should screw straight into the hole at the end of the tank outlet. If the threaded section at the back of tap is too small to screw into the tank outlet, use a reducing bush, a threaded plastic adapter that allows you to screw a smaller fitting into a larger sized hole.

irrigation-fitting reducing-bush
A threaded male-to-female irrigation reducing bush can be used to fit an undersized tap thread into a larger tank outlet

Instead of a brass tap, we can use a ball valve, which is much more durable, doesn’t need replaceable tap washers, and only requires a quarter of a turn to go from fully closed to fully open. Ball valves come in different sizes, and in this application we will use a 20mm ball valve.

ball valve
Ball valves can be used in place of a tap, these are more durable but also more expensive

Ball valves cost more than brass taps, and since these have female threads on both sides, they require an additional fittings to connect them to the tank.

To connect a ball valve with a female end to a threaded tank outlet, we will need a threaded nipple fitting, specifically a Hex Nipple 20mmx20mm BSP Irrigation fitting.

hex nipple 20mmx20mm irrigation fitting
hex nipple 20mmx20mm irrigation fitting has threaded male fittings on either side

Step 3 – Select Tools for Drilling the Holes

There are two tools that I would recommend for drilling large diameter hole into the plastic drum to fit the 20mm threaded tank outlet. Either a hole saw or a step drill will perform the task quickly and easily.

1.   25mm Hole Saw

hole saw
25mm hole saw with arbor

A hole saw is the recommended option, as it’s impossible to make a mistake with this one. Used with a cordless drill or regular electric drill, it leaves a slightly rougher hole, which can easily be smoothed off with a piece of rolled up sandpaper.

To cut a hole that will be a snug fit for a 20mm threaded tank outlet (which has an actual outer diameter of 25mm), you will need a 25mm hole saw.

2.   Step Drill

A step drill can make various sized holes, this one is a 10-30mm size

A step drill is also used with a cordless drill or regular electric drill, and leaves a very clean-cut hole with a smooth finish.

Since this drill is conical (cone-shaped) and the plastic of the drum is quite thick, it’s necessary to drill the hole from both sides to get a straight through cut, otherwise the hole will be bigger on the outer side.

Step drills are slightly more difficult to use as there is the ever-present risk of pushing the drill one step too far further and making the hole overly large. Only use a step drill if you have experience using these on thick plastic.

The hole for a threaded tank outlet is approximately 25mm wide, so the step drill will need to go larger than this at its widest point. The step drill I have used here is a 10-30mm step drill.

Step 4 – Mark the Position of the Holes for Drilling

Next, mark the location of the hole on the plastic drum. Pick a smooth spot on the side of the tank where there are no seams or ridges, to ensure a watertight seal when you fit the threaded tank outlet.

In this case I have chosen to drill the hole about 10cm (4″) from the bottom. The reason being that if I have a tap fitted to the tank, the tap is high enough so that I can place a bucket underneath it, without having to raise the tank too high off the ground.

Keep in mind that the higher the tap is mounted above the bottom of the tank, the more water will be left at the bottom that wont drain out!

DIY rainwater tank construction
Marking the location of the hole on the plastic drum

If you are fitting an overflow pipe to the tank, mark a location on the side, near the top of the plastic drum. Give some consideration as to where you place the overflow, as this will be the level when water will drain out of the tank, so the higher the better.

If the sides of the plastic drum slope in towards the top, take a moment to see how the Threaded Tank Inlet will best fit.

Step 5 – Drill Holes in the Plastic Drum

Drill the hole on the spot marked on the plastic drum.

  • If you used the hole saw, and there are any rough edges, smooth them down with a piece of sandpaper to create a smoother surface for a better seal. Test fit the the 20mm threaded tank outlet to ensure it fits snugly into the hole.
  • If you used a step drill, drill the hole bit by bit and test to see if the hole is big enough to accept the threaded tank outlet. The risk with a step drill is that you can go too far and drill an overly-large hole. What you want a snug fit! If it nearly fits, drill a bit further from the other side (inside of tank) to even up the hole, then test fit again. Repeat procedure until a snug fit is achieved.
DIY rainwater tank construction
Step drill used to drill hole in plastic drum

Step 6 – Fit Threaded Outlet to Tank

Screw the threaded tank outlet into the plastic drum.

I have chosen to put the shaft of the threaded tank outlet on the inside of the plastic drum, so the fitting can be as short as possible on the outside, to save space in the walkway where I’ve located the tanks.

With the short side on the inside the tank, it will be easier to get more water out of the tank, and pour out the very last bit by leaning the tank a bit sideways. With the short side on the outside, like I’ve done here, it wont be possible to do that.

Threaded tank outlet fitted into plastic drum (inside view)
Threaded tank outlet fitted into plastic drum (outside view)

Step 7 – Tighten Tank Outlet

Tighten the threaded tank outlet by using two adjustable spanners, one inside the tank and one on the outside.

Hold the one inside the tank in place with the handle pointing up to make it easy to reach it, and turn the outside one to tighten it. Tighten reasonably firmly but do not over-tighten!

NOTE: A fairly BIG adjustable spanner is required to fit around the hexagonal part of the 20mm threaded tank outlet!

Use an adjustable spanner to hold the threaded tank outlet inside the tank
The other adjustable spanner used outside the tank to turn the threaded tank outlet to tighten it

Step 8 – Fit the Tank Overflow Pipe

Even though it’s optional, it’s best to fit an overflow outlet, so when the tank fills with rainwater, the excess can be directed where needed rather than overflowing and running on the ground.

A length of flexible pipe can be connected to the overflow outlet to direct the water into the garden, a pond, water garden, or another tank.

Tank with water inlet in lid and overflow pipe on the left side

With the tap facing forward, locate the overflow pipe on either the left or right side of the tank, close to the top, on a smooth section away from any seams or ridges for a good watertight seal.

Completed overflow outlet on tank, with 22mm washing machine style flexible hose connected, running out to the garden

Here is a closer look at the overflow outlet, it’s identical to the lower tap outlet fitting, the only difference is that there is an 20mm elbow connected to the outside to keep the hose close to the side of the tank.

Another benefit of the elbow is that by turning it upwards, it will allow the water to reach a higher level in the tank before it flows out of the overflow pipe.

Overflow pipe mounted on the side of the tank near the top. In this picture, the end has a cap screwed on to shut it off because the overflow is not being used here, and this prevents entry of mosquitos

If you are connecting multiple tanks together, only one tank needs an overflow pipe connected, as all the tanks fill and drain simultaneously.

The whole setup behaves as if it were one large tank, with a single inlet where the rainwater comes in, and a single overflow to let out excess water.

Step 9 – Fit Rainwater Inlet to Tank Lid

With a single tank setup, you will need some kind of inlet where the captured rainwater enters. The style of inlet you choose will partly depend on the kind of lid your plastic drum comes with, as you’ll need to adapt it for your purpose.

You must use a lid in order to prevent mosquitos breeding in the water tank. Any holes in the lid need to be screened with a fine mesh (such as shade cloth) for the same reason. The fine mesh will also work as a coarse filter that prevents debris and dirt from getting into the tank.

NOTE: The lid cannot be airtight otherwise it will create a vacuum in the tank when water is drawn from it, and the resulting “vacuum lock” will stop the water flowing, so some kind of vent is necessary.

The lid on my tank came with a small screw top as pictured below:

Plastic tank lid with screw cap in the centre

Looking at the underside of the lid, I have regular clear silicone sealer to glue a 90mm PVC female gutter outlet over the hole.

Sitting to the right of it is a 90mm stainless steel mesh PVC fitting that can be plugged into the 90mm PVC female gutter outlet to act as a removable filter for the rainwater tank inlet.

DIY rainwater tank construction
90mm female gutter outlet siliconed to underside of lid, to hold removable filter, pictured right

Different tank lids will require different solutions. Don’t be afraid to innovate! Instead of the lid, a piece of shade cloth, flyscreen or similar material can be stretched over the top of the tank and tied in place it around the rim of the tank.

Step 10 – Assemble the Tank Stand

Construct a tank stand out of concrete blocks (Besser blocks). Place two side by side so they are wide enough apart to support as much of the tank base as possible.

Two concrete blocks used to elevate the tank

Place two standard rectangular pavers across the top of the concrete block to complete the tank base.

Water tank base made from two concrete blocks with two concrete pavers laid across them

Step 11 – Position Tank on the Stand

Position the tank on top of the concrete block stand.

Important – make sure that the bottom edge of the plastic drum is sitting on top of the pavers. The simplest way to do this is to position the base and the pavers so that the edges of the pavers extend past the tank bottom as much as possible. The edges of the plastic drum support the weight, and a full tank of water weighs 220kg!

Tank seated on concrete block base, with the paver edges extending past the tank base

Step 12 – Install the Tap and Overflow Pipe

If setting up a single tank, fit the brass tap or ball valve to the tank.

To fit the brass tap, wind Teflon plumbers tape around the threads to create a watertight seal (see instructions below), and then screw it by hand into the threaded tank outlet. Hand-tighten only.

Install any fittings required to connect a pipe to the overflow outlet, and use Teflon tape on any threaded (screwed in) joins.

The water tank should now be complete and ready to use!

How to Use Teflon Tape on Threaded Plumbing Joins

Here are a few tips on how to use Teflon plumbers tape on threaded (screw) joints of irrigation fittings to create watertight fittings that won’t leak: 

plumbers tape on irrigation fittings
  1. Begin by holding the pipe or fitting in the left hand with the end facing you (as shown in the picture)
  2. Hold the roll of tape so it looks like a snail, with the tape unrolling off the bottom edge (as shown in the picture)
  3. Lay the tape across the bottom edge of the pipe or fitting, then wind it on clockwise, moving upwards, in the direction of the threads, with a little bit of tension, for around 7 turns.

Wrapping in the direction of the threads is important, as wrapping the wrong way may result in the tape coming unwound as the fittings are tightened. Also be careful not to wrap over the hole.

You wind the tape clockwise so it stays on when you screw the fitting in, if you wind it the other way it will unwind when you screw it in. You hold it “snail-wise” with the tape feeding from the bottom so you can tension the tape as you wind it. If you hold it the other way the tape loops out faster than you can wind it and it’s impossible to tighten it as you wind it!

How to Connect Multiple Rainwater Tanks Together

In this set of instructions five tanks have been connected together across the bottom via the threaded tank outlet where the tap or ball valve is normally connected.

Instead of fitting a tap, a 20mm x 20mm threaded nipple is fitted to the tanks (just like when were attaching a ball valve tap) which allows us connect the tanks to a 19mm polypipe main supply line that connects to a pump.

Step 1 – Wrap Threads with Teflon Tape

On one end of the 20mm x 20mm threaded hex nipple fitting, wind around the threads with Teflon plumbers tape to create a watertight seal.

hex nipple 20mmx20mm irrigation fitting
20mm x 20mm threaded hex nipple fitting

Step 2 – Attach Fitting to Rainwater Tank

Screw the 20mm x 20mm threaded hex nipple fitting into the threaded tank outlet on the rainwater water tank, and gently tighten it with an adjustable spanner.

There’s no need to over-tighten the fitting because the Teflon plumber’s tape will create a tight seal with only a moderate amount of tightening.

DIY rainwater tank construction
Fitting wrapped with Teflon plumber’s tape screwed into threaded tank outlet for a watertight seal

To connect a 20mm threaded tank Inlet to a 19mm irrigation pipe, we can use a 20mm nut and 19mm tail, pictured below:

20mm nut and tail irrigation fitting
20mm nut and 19mm tail irrigation fitting can be unscrewed by hand

A nut and tail can be turned by hand easily to screw and unscrew it from the tank. It has a rubber washer to create a nice tight seal with minimum pressure. This is rather handy as you don’t need any tools to remove a tank from the outlet pipe.

Step 3 – Construct Adapter to Connect Tank to Other Tanks

The adapter can be made from a 19mm barbed T-piece, or T-joiner, a short length of 19mm irrigation poly pipe and a 20mm BSP Nut x 19mm tail, as shown below.     

Fit the Nut and Tail to the T-piece, the assembled adapter shown below:

Step 4 – Fit Adapter to Tank and Balance Pipe

Screw the adapter onto the tank, hand tighten, and push fit the balance pipe (which connects all tanks together) into one end of the T-joiner.

Adapter connected to new tank and balance pipe

Step 5 – Optional – Fit Siphon Pipe to Tank

This step is optional, but it’s one innovation that I invented that’s worth it’s weight in gold if you are using a pump. If you’re not using a pump, you might want to skip this step, thought it still has some benefits even when you just fit a tap to the tank.

One of the problems with having the outlet on the side of the tank is that you always end up with water below the outlet that you can’t get to, so it just sits there. No big deal with one tank perhaps, it may be just 20 litres. But when you have multiple tanks, this unusable residual amount adds up. With a six-tank setup like mine, that adds up to around 120 litres, which is equivalent to a half of a single tank!

The simple solution is to connect a 20mm elbow to the threaded tank outlet inside the tank, then screw in a short 20mm riser tube and push the end of the tube down so it touches the bottom of the tank, as shown in the picture below.

A short riser tube is attached to the end of the threaded tank outlet with a 20mm elbow join

With a pump connected, it works just like drinking with a straw, extracting every last drop of water out of the bottom of the tank.

Step 6 – Connect Rainwater Tank to Pump

Connect the other side of the T-piece to a short length of 19mm irrigation poly pipe, and connect an inline 19mm tap , then run the other side of the tap to the pump.

Balance pipe connected to tank, terminated with an inline tap, and connected to pump inlet hose

Step 7 – Setting Up the Pump

This is my pump setup. The white pump inlet hose is connected to a filter (bottom left) to remove any particles from the water, in order to prevent wear on the pump, and to prevent clogging in the drip-line irrigation system.

The green hose is the pump outlet. This pump has a manometer switch, the big yellow cylinder at the top – it’s a pressure activated switch that switches the pump on when you try to draw water, and switches off automatically when you stop. It all sits on a raised concrete plinth to keep the pump out of dirt and water on the ground.

Step 8 – Connect Pump to Tap

This is the complete pump setup. The plastic pump cover protects the pump from rain and sunlight. The pump is connected to an outdoor waterproof power inlet. The green outlet hose is connected to a tap mounted on the wall.

As the pump has a pressure activated switch, when you turn on the tap, it turn off the pump, and water runs, when you turn off the tap, it switches the pump off.

This system allows me to use the tap in the same way as the taps on the mains supply, the only difference is that this tap supplies rainwater from the tanks. Just like the mains water taps, I can connect a hose to it, fill buckets or watering cans, it works identically.

A closer look at the tap setup. I’ve chosen to use regular garden hose “click-fittings” for convenience to connect the pump to the bottom of the tap, and to connect things to the tap. I’ve drilled into the brickwork to secure the tap firmly, and used plastic plugs with screws to fasten it in place.

tap connected to pump on DIY rainwater tank

Explaining the Design Rationale

At this point I will explain some of the design of the multiple tank setup and the rationale as to why I’ve used the fittings that I have. feel free to skip this section if you so choose to!

The pipe that connects the tanks together is cheap 19mm black irrigation poly pipe. This is adequate to join all the tanks together and works reasonably well as a “balance pipe” which allows all the tanks to fill, and drain, at the same time.

The smaller 13mm irrigation poly pipe is not large enough and the flow is drastically reduced, so in a heavy downpour, the main collector tank (where the rain water flows into) will overflow because the thin pipe cannot fill the other tanks fast enough.

The bigger the pipe diameter the better, but if you use 25mm irrigation poly pipe, you have to use larger size fitting, and the cost of the larger size fittings starts to become prohibitively expensive, especially with multiple tanks!

So, using a 19mm irrigation poly pipe is the optimum size between cost and performance. When plumbing any pipes to supply water, you ideally want to keep the size of the pipe the same size, as using any fitting that narrower than the pipe size restricts the flow of water.

So what does this mean? If you’re using a pump with your tanks, the pump won’t be able to pump as much water, so you won’t be able to pump it as far, or the lengths of irrigation pipe/number of irrigation points that your pumping to, will be reduced. So it’s critical to not restrict the supply pipes!

So what does this mean for our project? Basically, you want to keep the inner diameter (the “hole size”) of any fitting at around 19mm. We’re using 19mm irrigation poly pipe, and a 20mm threaded tank outlet. If we are going to connect anything to this we want to keep the internal pipe diameter the same.

51 thoughts on “How to Make a Rainwater Tank from Recycled Plastic Drums

  1. I made a system remarkably similiar to this one. I used basically all the same fittings but have no tank. The tap you have going out to the pump is my outlet – note is has developed a small drip so we have to keep a bucket under the tap. My overflow is just a 20mm irrigation hose stuck through a hole that i drilled with a large drill bit and then siliconed the crap out of it on the outside, it is very flimsy and was a mistake in hindsight. The method you use is smarter. I chose not to use the same fitting because I wanted to put the overflow in a higher position, but I should have sacrificed a bit of storage for a more stable system. I also siliconed the inside and out of the fittings at the bottom of the tanks as a failsafe. All up my system cost $130 for 960L of storage. I like this method because you can add onto it so easily if you need to

  2. Hi Evan,

    I initially had a water leak problem when I used snap-on fittings to connect the balance pipe (the big long pipe that connects all the tanks together in the pictures shown) to the tanks. Incidentally, these are the same snap-on or “click” fittings like on a regular garden hose, I used the ones for 19mm irrigation fittings that connect to poly-pipe instead.

    The problem is that when you put any tension or flex on the hose so it pushes the snap-on connectors sideways at an angle, they leak! Solved the problem by using screw fittings that can be hand tightened.

    Also, I found that the threaded tank inlets dont need any silicone sealant to be watertight if you put the rubber washer or gasket on the inside, and the harder plastic one on the outside.

    Thanks for sharing your construction details!


  3. Hi Blackthorn,

    Its not the hose that leaks it is the tap, but it is no big deal, i can live with it. I just periodically pour the bucket that collects the leak back into the top of the system. I used silicon because I used olive barrels rather than the blue barrels that you have. There is an italian and greek food importer on Holmes street in Brunswick called Ausfresh that sells them at 4 for $50. The difference between these barrels and your tanks is that they have a much larger curve at the bottom. Because I don’t want to use a tank I had to put the threaded fitting as close to the bottom of the barrel as possible so we could access the water from the tanks at the lowest possible water level. Again this is all minor details but I think its great that we both essentially have the same system for the tanks. There are so many of these barrels around and this is a great way for gardeners to cheaply harvest rainwater.

    1. Hi Evan,

      Thanks for clarifying that, now I understand what you meant. I know what you mean about the olive barrels having greater curvature at the base, I’ve got one feeding half of my hydroponic setup. At the price that you’re getting them, I wouldn’t use anything else! Thanks for mentioning where to source cheap plastic drums from, a lot of people will find that very helpful, myself included. It’s great we’ve come up with a fairly similar design, as you have found, it works well, and is very cost effective.

      A friend had a few other designs, which we jointly further developed and refined, hopefully willwrite these up and share them soon.

      Thanks for sharing!


  4. Excellent article. Congratulations. It answers all my problems except one. I have in my garden a converted water drainage tank that went to the rain system. Local coungil regulation at the time the house was built. How can I get the threaded tank inlet into the inside of the tank when the tank has only a very small aperture at the top. I’m only a little, old ( 81) bloke but crickey!!
    Would appreciate any advice.

    Good wishes

    John Skull

    1. Hi John,

      Luckily you don’t have to get inside the tank! There is hope!!!

      The other way to do it is to use a brass tap, ball valve (a sideways sort of tap, as shown in the article) or whatever brass fitting you intend to use, which has threads on the end that can be screwed into the tank. Drill a hole a bit smaller than the threaded (male) section of the brass fitting – it has to be smaller to make a watertight seal, then screw it in. The brass is harder than the plastic and will cut threads into the plastic as you screw it in, for a perfect screw-in fit. If the wall of the platic tank is thick enough, it will hold quite securely. Make sure you use some kind of rubber washer to create a better seal between the tank and the tap/fitting. Even better is to use a little bit of clear silicone sealer around the fitting before it’s scewed all the way in, then add a bit more after it’s screwed into place. This will make for a very watertight seal.

      Hope this helps! May your rainwater tanks be always full!


  5. Hi There

    RE: A cheaper way to join your tanks.

    I made a distributed tank array which I posted at Initially the tank retailers put me onto the threaded fittings you used and I bought a few for a trial. When I bought the bulk of my barrels, Louis the seller told me about using top hat grommets with standard barbed T-joiner fittings. I used a mix of 25mm and 19mm fittings. You just place the grommet in the slightly oversized hole and then ram the perpendicular opening of the T into the grommet for a snug fit.

    I’ve had the array installed for a couple of years and it hasn’t leaked (at first there were one or two v slow dribbles but the self-sealed). I didn’t even need plastic hose clamps on the joining tubes (only under atmospheric pressure of water in tanks).

    I have 22 barrels there and others around the place so the cost saving was significant.


    1. Hi Alastair,

      Thanks for sharing this information and the pictures, I must say that’s a very impressive array of water tanks you’ve set up!


    2. Hi Alastair
      I have not been able to see a picture of your water barrels at the link above? I saw somewhere that you are in East Bentleigh which is close to me in Hampton East. Is it possible for me to have a look at you barrel water system as I would like to set something up and have no idea where to start. Do you know where to get the blue barrels at the top of this article?

  6. Thanks for sharing your setup and how-to. We have 6 olive barrels (and @ $10 each I reckon it’s a pretty cheap way to set up water storage) and I’ve been sitting out the back pondering them, taps and all the other bits.

    As mentioned above the olive barrels are quite roundy with a slight ridge here and there. I don’t really want to put the tap on the curve, so it means it will be slightly higher. I’m aiming to not run a pump (as appealing as it might be) for power/kid reasons.

    I want to just get two barrels up and running for water, at this stage as the others have been set aside for flour, oats etc storage so we can purchase them in bulk and have somewhere to put them.

    I’ve got a busted back screen door so can easily source the mozzie-proofing stuff. I just need to work out the ‘how’ so your DIY sharing has come in handy to give me an idea of where to start.

    I’ll be off to Bunnings with toddler in tow while the others are at school, to see what I can come up with.

    Cheers for sharing.


  7. Hi Kirsty

    I recommend you just use Top Hat grommets and barbed 19mm T-piece fittings (or 25mm if you really want to). Much cheaper than the threaded ones and quicker too. They’re totally acceptable and I’ve used tried both methods.

  8. thanks for the recommendation Alastair. I’m not in Vic, though might just compare the prices anyway and see if it’s still cheaper with postage.

  9. Alastair we’re getting started on ours – yay! Now, this may be a long shot but I am trying to show my husband the page where a guy has stacked barrels (blue?) roughly ten along the bottom and ten along the top… I was sure I bookmarked it but no. If by chance you know the page and can post the link that’d be great.

    Like I said, long shot 🙂 Thanks for your help so far, it’s been great to find your post and nut out ideas.

  10. Sorry, no KIRSTY. Be aware that when you stack, sealing the barrels on the bottom row is tricky. Mine wouldn’t seal despite concerted effort on my part (mallets and the like!).

    That means a shut-off valve so when the bottom barrels are full water is only feeding the top row.

    I set my system up to have +two+ bottom levels (about 4″ step up/down) and therefore two top levels to account for the fall in slab, so that doubled the shut-offs (and separate take-off ) to four valves of each. I used sand to account to get the same level in each set, about 2″ deep at the thickest part.

  11. Hi Alastair. Would you believe that I came to your site to find something for Kirsty, but she beat me to it!

    Was at your place a few months ago with some guys from the East Bentleigh SGA pod. I was very impressed with your setup and am attempting to do the same thing at my place.

    I run a volunteer group that collects used coffee grounds and then uses them for composting, and there was a lady helping you out on that day that was interested in starting something over your way. Having done this for over a year now, I can recommend it as an effective and cost free way to add organic material to the garden.
    If you guys are still interested (and hope you are!), stop by the site or send me an email. I still owe you from that visit so let me return the favour.

    1. Hi Alistair. Please send me the contact details so I can join the East Bentleigh SGA. Thanks

  12. lol how cool – small world eh, as they say!

    Thanks both of you – I’ll keep hunting for that photo and if I ever find it will post back here.

    Alastair thankyou re the stacking information. Will keep in mind if we get that far. Atm we have the barrels lined up, ready to go, with some of the ‘plumbing’ in… the challenge is our silly downpipes which of course (consistent with the rest of the house) are ~not~ standard issue. So we’re making things we need as we go.

    Cheers again, both of you 🙂

  13. Just thought I should state that I, Alastair Leith am not the author of this blog. I just commented on a cheaper (and easier) plumbing method and linked to my project as shown on You can find the link above.

    Blackthorn seems to be the author of this very useful and well presented site. 🙂

    Nice work, @Kirsty. So nah, you don’t wanna be storing and eating that much refined white flour it’s really not so good for us, much better as water tanks. 🙂

    My other gratuitous advice while I’m on that health themeand this is a total thread-jack so I’ll make it brief please read The China Study by Prof/Dr Colin Campbell. I am and am I’m loving it.

    My friend who eats mainly raw fruits and vegetables dad is a GP and started reading it when he was baby-sitting my friends kids. I blew him away that he had never heard most of this stuff in med school and the journals. (GPs only have a one to two hours lecture on nutrition in almost all Medical Degrees the world over so no great surprise to me).

    So much of what we hear in the media and even some authentic science discourse (opposed to straight out marketing lies) is hiding the great harm that so much of the SAuD diet is doing to our collective health. In short animal protein and fats esp dairy implicated in almost every major disease in the Western and now parts of developing world from heart disease and cancer, to MS and Kidney stones to Alzheimer’s and osteoporosis yes cow’s milk +weakens+ human bones).

    Definitely read if you are raising a family. You might already know this but I just read some more of it his book today and wanted to share! 🙂

  14. Ah Alastair, well then my correction – thanks to Blackthorn, absolutely for the information and pics in this informative blog post. Also for being so kind-hearted as to not make a big deal out of my mistake! 🙂
    Thanks a bunch for all the information *nods*

  15. Hi guys, yes, this is my website!

    Thanks Kristy for the welcome feedback, and thanks Alastair for your ideas and suggestions.

    I have two other tank designs from a while back, will hopefully publish the articles soon!


  16. Thanks Blackthorn. It was ~great~ to have all the info in your post to go through and ponder over when working out how to do ours.

    Looking forward, when you can, to seeing your other tank designs 🙂

    Kind Regards and thanks

  17. I have a question regarding drip irrigation and rainwater storage tanks.

    I live in rural France, and because of my work I have to be away from home for a week or more at a time, starting in mid March and throughout the summer. This makes it hard for me to get a vegetable garden established, especially if the weather turns dry while my seeds are germinating or the seedlings just getting going; which happens often enough around here. I can’t put in a regular timer and watering drip system on my pressurized household water, because that would require me leaving the tap open all the time and for reasons I won’t bore you with, the pressure is such that it leaks constantly. I don’t want that water leaking by the wall of the house while I’m gone.

    Anyway in short I’ve been told that under realistic situations, gravity will not be enough to run a timer. If I just water constantly at a low volume (eliminate the timer), can a reliable drip irrigation system work with a water tank a couple of meters above the ground, for example? Would this work, in your view? Or would this constant watering be harmful for most vegetables?

    Thanks for any advice you can give,


    1. Hi Kathy,

      You can put a pressure reducer, in fact, you should always put a pressure reducer on your mains water supply drip system a the tap before the filter, and this will eliminate any issues with excessive pressure.

      If you are choosing to use gravity fed irrigation from elevated tanks, you actually can get a low pressure tap timer which is designed to be fitted to gravity feed systems or a low pressure rainwater tank.

      Note, when using gravity feed you can’t use standard drip line irrigation, that requires a certain level of water pressure to run unless you are driving it with a pump. If you choose to gravity feed, you will need to use specific gravity feed drip line which has larger holes to allow it to operate correctly under low pressure.

      Hope this helps.

  18. i have a rain barrel system in place and was wondering what type of pump would i use for pumping water to wash the car and the windows on the house and also a power gun for washing the decking.

    1. You can connect a pressure sprayer directly to the tank, they are able to draw water from a container as the pressure sprayer is really just a pump!

  19. Wonderful ideas! I have heard that placing plastic barrels directly on cement is bad for them, the lye in the cement eats away the plastic over time. Have you had any problem with this?

    1. Hi Kristiane, I can clarify one point, the two words sound the very similar, cement actually contains ‘lime’, not ‘lye’.
      I have not heard of the lime in cement affecting plastics, my tanks are all placed on ‘besser blocks’ which are made of concrete and I have not noticed any effect over the last five or six years.

  20. Hi Angelo,
    You have an amazing garden. I got to see it in the flesh last summer at one of your open days after a few years ogling it in the photos. It was like meeting one of the early rockstars from the 60s.
    I have a vague question you might be able to answer, as the curator of a functioning food-forest. How much water do you think you irrigate into your garden over the dry summer months, say November-March, in the last couple of years since the garden has become more established? Say, litres/square meter/per day or per week. I’m trying to get a feel for how much water consumption would be needed by a functioning food forest with dozens of close trees in those summer months, in your Melbourne climate. The amount of rainfall has fluctuated pretty wildly over the last few Januaries and Februaries, but wondering if you can give some kind of ballpark figure? I’m trying to get ideas for how realistically one could rely purely on rainwater catchment to feed into the garden over the summer months. Thanks a lot

    1. Thanks James!
      With the garden I run the irrigation during the warm season from November till March (late spring to early autumn) on an automated cycle of two 50 minute waterings a week to supplement the rainwater I capture (2,000L is all my tanks hold which is captured from a 30sq m garage roof – very small scale) and use in the garden. As you mentioned the rainfall this year has actually decreased, which is a bit of a worry. The only way I can work out what that translates into water volume is to work out the exact length of dripper irrigation in the garden, knowing there is a dripper at every 30cm that has a dripper flow rate of two litres per hour. I’m not sure how much I used, but there can not be more than 60m on any one circuit and I have two circuits.

      Also keep in mind that my garden is fully north facing so it faces the summer sun head on (southern hemisphere) and there’s a fair bit of concrete and brickwork, so there is a lot of reflected heat, and the garden is terraced on a sloping block with an alluvial sandy loam, so the drainage in the soil is possibly higher, but I usually mulch heavily to minimise evaporative losses and the dripline irrigation sits below the mulch. You also need to take into account factors such as these when determining your own garden’s water requirements.

      Regards, Angelo

  21. Hello!
    Great post, thank you!
    A short question: where can one buy a threaded tank inlet online? I’m from Europe an “local stores” don’t have this..

    1. You’re welcome! Well, Europe is a mighty big place and I’m on the other side of the world, so I can’t really help much there, but I would look for a plumbing supplies shop if that helps.

  22. Where can we purchase the 20mm inlet tank bulkhead plastic fittings? Please lead us to a website as we are in the US-Thanks

    1. Sorry I can’t help, we’re an international website but I’m in Australia, approximately 9,463 miles or 15,230 km from the US! I don’t get to shop there often! Try any store that sells water tanks and fittings, or a plumbing supply shop.

      Since measurements aren’t metric in the US, you need to use imperial measurements when doing an internet search, look up a 3/4″ bulkhead tank fitting and you’ll find plenty of US suppliers.

  23. You can get most or all of the equipment for free from Gumtree if you keep checking over time. You can even put up a wanted ad for them and probably someone will be glad to give them away and avoid paying to take them to the tip.

    I have the space but my wife won’t accept it because she’d find it ugly (along with compost bins, worm farms etc.).

  24. Gidday, epic documentation! well done. Much complexity and cost can be avoided in linking tanks by simply connecting them with siphoning pipe permanently keeping the water the same level in each tank.

  25. I just set this system up a couple of weekends ago with 4 barrels. Very easy!! I’m a 59 year old female and I did it all on my own. The only challenge I had was drilling and screwing the gutter filter onto the gutter – couldn’t see the holes and screws with my glasses on or off. LOL!!

  26. Just wanted to say thank you for this excellent post, I just completed the first stage of a 5 barrel system. I only have about 900mm down that side of the house and I got a quote for a custom made tank to fit the space – 2000L would cost nearly $3,000! I’ve now spent about $200 and have about 1000L thanks to this page.

    Given the space constraints I had to plumb them directly into each other in series, which made installing them a bit tricky but we got there in the end. I used the top-hat grommet method mentioned by Alastair and found it worked really well, I purposely drilled the holes a bit small which meant I needed quite a bit of force to get the barbed piece into the barrel but once it was in it wasn’t moving. A bit of sewing machine oil really helped in that regard.

    At the moment its working off gravity, takes about 20 seconds to fill a 9L watering can (tanks are full to the brim at the moment), I’m constantly scouring Gumtree looking for a second-hand pump so I can run a hose off it (that will be stage 2).

    Many thanks again!

  27. Hi, just came accross this post as I am trying to utilize some permaculture design ideas in our backyard. We live in Ireland so it rains a lot but lately (few last summers) water started to become an issue. So while it is still spring I’m hoping to put together a rainwater harvesting system.
    I am just wondering about the blue barrels. There are some on offer on a local buy and sell page but it used to store AdBlu (diesel additive in it) . I cannot find info on if it can be washed out and use. What do you reckon? Thanks 🙂

    1. The blue drums I used for water tanks once had laundry detergent in them, that’s not really too hard to wash out, and not really toxic, all you need is water to wash them out but it creates a lot of soap suds. The smell, or the fragrance to be more precise, took months to disappear, so no matter how well you wash the tanks, you never get them totally clean.

      I definitely wouldn’t use anything that contained any nasty chemicals like diesel additive, you don’t want that contaminating your soil, and that would be a nightmare to wash out. Unless you can find blue drums that contained soap, go for the brown drums that are used for food, I have three of these, and the lids are better because they screw on.

  28. HI! My house has got 8 downpipes, at equal distance. Im guessing it must have been similar on your house, but I see only a single downpipe intake. Did you block the other downpipes or did you build a system to bring all the water to your tank array? This is some amazingly well done documentation, thanks!

    1. Hi Mat, I’m only capturing off a large 30 sq. metre garage roof which feeds into a single downpipe.
      My house has four downpipes, one near each corner. Each downpipe will supply a quarter of the total rain falling on the roof if I tapped into them to harvest rainwater.

      I’ve seen devices that fit into the holes in the gutter to elevate the level so that rainwater has to rise above a certain level before it drains into the downpipe. One gutter opening is not fitted with the level raising device so most oof the water drains down a single downpipe.

  29. Hello there, just want to ask, haven’t you have any problems with the inflow of water on the other drum since it is all located at the bottom?

    1. No, water naturally flows to the lowest point by gravity, so the full tank flows into the empty tanks through the balance pipe at the bottom until they all reach the same level.

  30. Hello from Cape Town, South Africa. Love your website and it’s intentions and wish you all success in your endeavours to educate on sustainable living. We live in a water-stressed area and I am keen to explore use of alternative water supply options. Would you have any guidance on use of GREY water in food gardening? Intuitively I would expect there to be severe limitations. However I would hate to let a resource go untapped due to ignorance. Most articles on the web tend to be very general and of limited use unfortunately.

Leave a Reply to keith walkerCancel reply