Recycled Plastic Drum Rainwater Tank

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

Why Small Size Water Tanks?

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!

You’ll hear many opinions about what size rainwater tanks are “worthwhile” and you’ll hear mention 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!

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, he’s the water-expert, and he 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.

Modular Water Tank System Construction

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:

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 Plastic Drum

Obtain a plastic drum with a lid, to use as your water tank. Clean and rinse out if necessary.

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

Recycled plastic drum (220 litre capacity)


Step 2 – Gather Tank Fittings

You will also need some tank fittings to construct your water tank.

For the basic single tanks design, you will need:

1.   20mm Threaded Tank Inlet (Bulkhead fitting).

These are used to attach connections to the tank.

You will need two of these, one to attach a tap to the tank, and another to attach an overflow pipe to the tank (if you choose to use one).

2.   Brass tap or Ball Valve.

When buying a tap, make sure you pick one with the right sized outlet (the side where the water comes out, where you would connect a hose), as they come in two sizes, 3/4″ Outlet and 1” Outlet.

I believe that the standard brass garden tap size used in all states of Australia is a 3/4″ Outlet, except in NSW. For NSW use the 1″ Outlet tap.

If your tap inlet (back of tap where water comes in from) is too small and doesn’t screw straight into your Threaded Tank Inlet, you will need a Reducing Bush, which is simply a threaded plastic adapter that allows you to screw a fitting into a larger sized hole.

Reducing Bush allows you to fit a smaller tap inlet into your tank’s Threaded Inlet

You can also use ball valves in place of a tap. They are very durable, and have a ¼ turn lever, which, as you’d guess, requires only a quarter of a turn to go from fully shut to fully open. In this application you would use a 20mm ball valve.



Ball valves are much more expensive than taps, and these female-female ball valves pictured below will require additional fittings to connect them to the tank.

To connect a ball valve with a female end to the Threaded Tank Inlet you will need a Threaded Nipple, specifically a 20mmx20mm Threaded Nipple, pictured below:

You can choose any style tap, from the common brass garden taps (pictured left) to the compact 1/4 turn lever handled tap (pictured right). These are fairly cheap, and if you select the right size, it will screw straight into the Threaded Tank inlet.


Step 3 – Prepare Drilling Equipment

There are two tools that I would recommend to drill a hole into the plastic drum to fit the 20mm Threaded Tank Inlet. Either tool will do the job well enough.

1.   Hole Saw.

The most recommended option, as it’s impossible to make a mistake with this one.. This is used with a cordless or regular electric drill, and leaves a slightly rougher hole that can 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 Inlet (which has an actual outer diameter of 25mm), you will need a 25mm Hole Saw.


2.   Step Drill.

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

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

This is slightly more difficult to use as there is the ever-present risk of pushing the drill one step further and making the hole too large. Use only if you have experience with Step Drills in thick plastic.

The hole you will be drilling for a 20mm Threaded Tank Inlet is approximately 25mm wide, so you will need a step drill that will go larger than this. What I’ve used (pictured below) is a 10-30mm Step Drill.


Step 4 – Mark the Location 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 Inlet.

In this case I have chosen to drill the hole about 4″ (10cm) 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 the tap, without having to support the tank too high off the ground.

Remember, the higher you mount the tap, the more water will be left at the bottom of the tank that you won’t be able to use!

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 Plastic Drum

Drill the hole on the spot you have 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.

If you use a Step Drill, drill the hole bit by bit and test to see if the hole is big enough to accept the Threaded Tank Inlet. The risk with a step drill is that you can drill the hole too large! You want a snug fit!

If it nearly fits, drill a bit further from the reverse side (inside of tank) to even up the hole and test fit to see if the Threaded Tank Inlet can now fit in. Repeat procedure until you get a snug fit.

Step Drill being used to drill plastic drum


Hole drilled for ready to accept the Threaded Tank Inlet


Step 6 – Test Fit Tank Inlets

Test the size of the hole to ensure that the 20mm Threaded Tank Inlet fits in snugly.

Test fitting the Threaded Tank Inlet


Step 7 – Fit Tank Inlets

Screw the Threaded Tank Inlet into the plastic drum.

I have chosen to have the tail or shaft of the Threaded Tank Inlet extend inside the plastic drum, so I can have the fitting as short as it can be on the outside, just to save space in the walkway where I’ve located the tanks.

If you put the short side inside the tank, you’ll get more water out of the tank, and it’s easier to pour out the last bit by leaning the tank over a bit. If you mount the long side in like I’ve done here, you won’t be able to do that.

Threaded Tank Inlet fitted into plastic drum (inside view)


Threaded Tank Inlet fitted into plastic drum (outside view)


Step 8 – Tighten Tank Inlets

Tighten the Threaded Tank Inlet by using two adjustable spanners, one inside the tank and one outside.

Hold the one inside still with the handle pointing up so you can reach it, and turn the outside one to tighten it. Tighten reasonably firmly but do not over-tighten!

NOTE: You’ll need a fairly BIG adjustable spanner to fit around the 20mm Threaded Tank Inlet!

One adjustable spanner to hold the Threaded Tank Inlet inside the tank


The other adjustable spanner is used outside the tank to turn the Threaded Tank Inlet to tighten it


Step 9 – Fit Overflow

If you are just setting up a single tank, even though it’s optional, it’s best to fit an overflow outlet. This way, when the tank fills with rainwater, rather than overflowing and running on the ground, you can take the overflow and run it via a length of flexible pipe into the garden, a pond, water garden, or another container.

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


With the tap or outlet on the tank facing you, locate the overflow pipe on either the left or right side of the tank, close to the top, and on a smooth section away from any seams or ridges.

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


Here is a closer look at the overflow outlet, it’s identical to the 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 his prevents entry of mosquitos.


If you are connecting together multiple tanks, 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 10 – Fit Rainwater Inlet

With a single tank setup, you will need some kind of inlet where the rainwater comes in. 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 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 you’ll create a vacuum in the tank when you draw water from it, and the “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:

I have used regular clear silicone sealer to glue a 90mm PVC Female Gutter Outlet to underside of lid.


A 90mm stainless steel mesh PVC fitting plugs straight into the 90mm PVC Female Gutter Outlet to create a filter for the rainwater tank inlet.


Different tank lids will require different solutions. Don’t be afraid to innovate and invent!

Instead of the lid, you can stretch shadecloth, flyscreen or something similar over the top of the tank and simply tie around the rim of the tank with a piece of string. The possibilities are endless!


Step 11 – Assemble 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.

Tank base made of two concrete blocks (Besser blocks) with two concrete pavers laid across them


Step 12 – Position Tank

Position the tank on top of the base.

Important – make sure that as much as possible of 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 stick out past the bottom of the tank.

(The rest of the bottom of the plastic drum is not critical, the edges supports all the weight, and a full drum of water weighs 220kg!)

Tank located on base, note that the edges of the pavers extend beyond the base of the tank


Step 13 – Install Fittings

If you are just setting up a single tank on its own, fit the tap to the tank at this stage.

Take your tap and wind around the threads with Teflon plumbers tape to create a watertight seal (see instructions below), and then screw it by hand into the Threaded Tank Inlet. Hand-tighten only.

Install any fittings require 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!



Handy Tip: Using Teflon Tape on Threaded Plumbing Joins

A few tips with using Teflon plumbers tape: 

Begin wrapping the threads from the end and wind down.the length of the fitting or pipe (as shown in picture).

Wrap in the direction of the threads. Wrapping the wrong way may result in the tape coming unwound as the fittings are tightened.
The simplest way to describe this technique is with a few steps for a right handed person.Hold the pipe or fitting in your left hand with the end facing you (just like the pipe in the picture)Holding the roll of tape so it looks like a “snail”, with the tape unrolling off the bottom edge (as pictured), wind it on clockwise with a little bit of tension, for around 7 turns.

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!



Connecting Multiple Tanks Together & Additional Tank Enhancements

The tank I have assembled in this set of instructions is to be connected to 5 other ones I have previously set up, so I’ll just be adding a connector to plumb it in to the main supply line of the pump.

Instead of fitting a tap, I’ll use a 25mm x 20mm Threaded Reducing Nipple to connect it to the main supply line of the pump

25mm x 20mm Threaded Reducing Nipple


Step 1 – Prepare Fitting

On the smaller end of the 25mm x 20mm Threaded Reducing Nipple, wind around the threads with Teflon plumbers tape to create a watertight seal.


Step 2 – Attach Fitting

Screw the 25mm x 20mm Threaded Reducing Nipple into the Threaded Tank Inlet and tighten with an adjustable spanner. You won’t need to over-tighten the fitting because the Teflon plumbers tape will create a fairly tight seal with only a moderate amount of tightening.

25mm x 20mm Threaded Reducing Nipple screwed into the Threaded Tank Inlet

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.

If you use the smaller 13mm irrigation poly pipe, it is far too small and the flow is drastically reduced, so in a heavy downpour, your 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 Inlet. If we are going to connect anything to this we want to keep the internal pipe diameter the same.

To connect a 20mm Threaded Tank Inlet to a 19mm irrigation pipe, we can use a single fitting, a 19mm tail x 20mm BSP male director, pictured below.

The downside is that we cannot easily disconnect the tank by hand if we need to.

We can use a fitting called a Nut and Tail instead, pictured below:

A Nut and Tail can be turned by had to screw and unscrew it from the tank. It has a rubber washer in it to create a nice tight seal with minimum pressure. This is rather handy as you don’t need any tools to remove a tank.

To connect the Nut and Tail fitting to the tank, you need an adapter which has male threads on either side, this fitting is called a Threaded Nipple, pictured below:

During the design process, I figured that since the Nut and Tail is hand tightened, it would be easier if the “nut” part was a bit bigger to get a better grip on. This is easily achieved at no extra cost.

Instead of using a 20mmx20mm Threaded Nipple to join the Nut and Tail to the tank, we can use a 20mmx25mm Threaded Nipple. It’s actually called a 25mm x 20mm Threaded Reducing Nipple (pictured below), but we’re using it the other way round to “expand” the size of the connection.

If we use a larger Nut and Tail, a 25mm BSP Nut x 19mm tail, the “nut” part is larger, so we get a bigger grip, which is easier to turn.

I hope that was not too confusing and explained my reasoning for this aspect of the design!


Step 3 – Construct Adapter to Connect Tank to Other Tanks

The adapter is made from a 19mm barbed T-piece, or T-joiner (pictured left), a short length of 19mm irrigation poly pipe and a 25mm BSP Nut x 19mm tail (pictured right).


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 Inlet 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.

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


Step 6 – Connect Tank Adapter 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 – Set up Pump

This is my pump set-up. 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, it 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.


In Conclusion…

Well, that’s the whole design, from the recycled drum to the fitted tap, and everything in between. Your setup doesn’t have to be this fancy to collect rainwater. A bare plastic drum or old wheelie bin under a broken gutter pipe will collect rainwater so too. All the fittings, pumps, etc. are all about convenience. Simply do what you can, start simple if that helps, and then experiment to see if you can do things better.

My first attempt at rainwater harvesting was with a converted wheelie bin that sat under a cut off gutter pipe, and guess what, it worked great! And if you’re wondering, here it is, and I still use it!

I’ll post the design for this wheelie bin water tank soon!

In the meantime, get out there and harvest all that free rainwater that nature bestows us with, and make a difference, every little bit counts!




  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.


  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 theme—and 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.

    Liked by 1 person

    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?

    Liked by 1 person

    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

    Liked by 1 person

    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..

    Liked by 1 person

    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.


    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.


  22. 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.).

    Liked by 1 person

  23. 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.

    Liked by 1 person

  24. 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!!

    Liked by 1 person

  25. 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!

    Liked by 1 person

  26. 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.


  27. HI! My house has got 8 downpipes, at equal distance. I’m 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.


  28. 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.


  29. 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.


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