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All up we've spent a bit under $1500 for about 3300 litres of storage that fills off less than 20mm of rain. The initial cost was $472.55 for 1000 litres of tank capacity, one drum per downpipe but I bought some extra stuff and some stuff that I wouldn't buy again. Lots of commercially installed systems use one big tank instead, but only connect it to one or two downpipes so you miss a lot of collection area. We have drums everywhere instead.

I bought 5 200l drums from the drum man 137 Bakers Rd Coburg (M Schott - Steel and Plastic Containers, 9354 4833. AussieWeb have a whole section of drum recyclers!) I could only fit five drums on the bike, so that's what I bought - $20 each. We could have bought a 1000l tank from Bunnings for $499, but it would have cost another $80-$100 for plumbing bits to get it installed and working, assuming we used free pallets to chock it up to avoid needing a pump or stand. A basic hand pump is about $100 on eBay but that seems ridiculous, there's got to be a cheaper option.

Next step: more tanks I think. Right now it takes less than 10mm of rain to fill all our tanks from empty, and once the garden is planted I think we'll be using at least 100l a day to water everything.

Later: Bought a 2100 Litre tank

We've added a 2100 litre tank from GreyTone.com.au for $800 including an electric pump that I'm using to move water from the 200l drums into the tank. That way we get max collection area without having to redo all the stormwater pipes. So I've also make a wee carry handle for the pump and added a switch so I can wander from drum to drum dragging the hose and extension cord, pumping drums into tank. That's becauase with small hoses (12mm) I can't suck water out of the tanks very well, so a short suction hose is better. Ideally I'd have an immersion pump but that's more expensive. If you have a list and visit a plumbing supplier like Reece's you can probably get reasonable prices just for knowing what you want.

Now that I've done much more internet searching I've discovered that we could have done things better or cheaper by buying only what we actually needed (rather than experimenting), and missing out some of the stuff that hasn't worked. Really.

Specifically, Nylex do make a big size click-together system, 18mm instead of 12mm called Maxi-flo but good luck finding it, even online. Bakers in Blacktown NSW would be one place to start. Turns out Bunnings stock them, prices reasonable but they didn't have the critical male tap adapter (but they sell a male-male 25mm or 20mm adapter in the plumbing bits section). Bunning prices are: $3 for a tap adapter: $10 for a kit with two hose ends and a tap adapter; $60 for an 18m hose with fittings and a trigger gun; $90 for a 30m hose with bits (the 30m hose is worth it, you can cut it down if you want to). Tank outlets are hard to find, but WetEarth have them for $8 each (but their website times out a lot for me so ring them 02 6009 0911) and Plastic Pipes wholesale them. Or you can get 25mm threaded ones from Irrigation warehouse.

Ideally I would start by doing this on each collection drum:

  • 90mm PVC pipe from gutter to about 2cm above inlet filter - so it just barely clears the top of the tank
  • optionally a 22.5 degree bend to make the drop into the tank easier
  • 300mm round inlet filter (drops in, easy to remove)
  • 90mm PVC 90 degree elbow to direct overflow down into stormwater system.
  • 90mm pipe to connect above bits up (about $30/6m length)
  • 25mm threaded tank outlet
  • 25 mm tap or valve
  • 25mm thread male-male adapter
  • 25mm Nylex Maxi-Flo adapter
That lets water flow in and out and gives you an easy connection at the bottom. The only hassle is that filling a bucket from the tank is mildly trick as the water comes out horizontally. Easy fix is to make a short (50cm) hose with one MaxiFlo connector on it. For the overflow I also cut a bit of plastic out of a takeaway container and use silion sealant to attach it over the overflow, so that only the top 3cm of the pipe is open. That gives another 15 litres capacity for each tank at the risk of overflowing in heavy rain. I think that any rain that heavy will make a bit of overflow from the tanks irrelevant. Some people don't hook the overflow into the stormwater system at all for this reason.

Overflow tanks just add capacity by connecting to an existing drum. The easy way is to use two tank outlets at the bottom of the drums and just pipe them together. But any failure in there empties both tanks. The safer way is to put a bit of pipe at the top, and I've just been drilling 90mm holes (using a $10 holesaw from Mitre 10 that's designed for installijng ceiling downlights - a proper bimetal one is over $100). Anyway, two 90mm holes at the same height and a bit of 90mm PVC pipe gives me a tight press fit (ie, hard to get the pipe in there) and so far they have not leaked. Even if there's dripping, you only lose the very top of the tank. I silicon seal them anyway.

  • two barbed 25mm tank outlets
  • 20cm of 25mm clear pipe
Make sure the bungs at the top of the drums are loose or the airtight drum will not fill.

Pumping into the big rainwater tank is easy enough - instead of a bucket under the drum/tap you have a pump. You'll need to connect a 25mm male thread on the drum to a 25mm female pump inlet. In theory a couple of barbed connectors press fitted into a 25mm pipe will work. But to screw it on or off you have to rotate the pump, which is tedious. So I use the Nylex connectors and make up a Nylex to pump fitting which also gives me a short bit of clear tube so I can watch the water flow. Then the pump outlet (25mm male thread) goes to another Nylex connector and a hose to the big tank, which is set up just like the drums.

  • 25mm barbed connectors, one male, one female
  • 18mm hose, 20-50cm long with Nylex MaxiFlo connector on each end
  • 25mm clear pipe about 15-20cm long
  • Nylex MaxiFlo hose long enough to go from any drum to your big tank

My system actually uses 12mm Nylex connectors and hose so it's cheaper but the flow rate sucks. The pump is doing less than half the throughput it should, just because the pipes are too small. Since you only need one tap adapter per drum/tank plus two hoses, going to the 18mm stuff shouldn't cost very much more than 12mm stuff. Online prices for this stuff are significantly better than street, which surprised me because I didn't think internet retailing of garden stuff was very advanced.

More description with each photo.Basic water tank, no overflow or tap fitted.\nThere's a stand roughly 300mm high so that the bottom is higher than the top of a bucket. This lets me siphon water out until the tank is empty, or fit a tap to do that more easily. \nThere's a proper leaf filter on the top and the downpipe fitting is screwed onto the house, so it should actually stay there. Detail of how the downpipe is attached. I can pull the pipe out if I need to as it's only held in place by friction. Filter on top of the tank. This also allows me to squeeze in there and get at the bottom of the tank. Which makes adding taps much easier. Note the adjustable leg (two of them are like that) so that I can level the tanks. Stand details. Simple layout, mostly made from scrap steel that I found around the place. Phuong welding legs for a tank stand. Rain!\n\nThis is when the tank was on the ground while I was playing with ideas. Hence the large gap between tank and pipe. Testing overflow ideas. I bought a really cheap 90mm holesaw ($10) designed for putting in downlights and it's working really well. The 90mm hole is a tight fit for 90mm downpipes, and they don't leak. Press fitted 90mm elbows drip a bit, but I'm leaving them unglued for now because I'd rather put a bucket under the tank than not be able to move them (it's a pain to push the pipe into the tank because it's such a tight fit, and I'm not sure i could do it with a tank on the other end of the pipe). The two elbows allow for slight alignment isses and it's cheaper than using flexible pipe. The finished tanks. Well, unless I decide to improve them.\n\nNote the new stand with two tanks on it,buckets under the dripping bits, and signs of rain. It was raining when I took the photo! Yay!\n\nThat tap is cheap but often drips when turned off. So I bought some expensive brass ones for the rest of the tanks. A completed tank. Note the somewhat contorted overflow that sends excess water to the stormwater system. The brass tap is screwed onto a 6cm-ish length of brass threaded pipe and a nut each side holds it into the tank. To seal it properly I cut a "washer" out of the tank lid and used silicon sealant to attach that to the tank. It means there's about 10mm of wall thickness there giving things a bit of rigidity as well as leak resistance. Seems to work :) Simpler version, the existing downpipe had a 90mm round entry to the ground so I just poked my overflow into that. Last thing to note is that the old downpipes are all still there and I have all the bits that I removed labelled and stored so I can pull the tanks out and return everything to stock. rental houses are a btch like that, I don't think the owner will agree to pay for the tanks. We buy mushroom compost for $2/tray and keep it in a dimly lit room until the mushrooms stop growing, then use it for compost. We get more than $2 worth of mushrooms from each container. The pump... pumping. Emptying the small drums into our big 2100 litre tank. Which is now full, so now we just wait for more rain to fill the last 800 litres or so of drums then it's all over until we use the water. We're planting garden as fast as we can to that end. Connecting a drum to the pump is a bit annoying, especially since I'm unwilling to pay for proper suction hose. So 20cm of 25mm pipe then convert to 12mm hose which plugs into the tank. It does work. I added the grey switch box so we can turn the pump off from this end. The blue thing on top of the pump is a controller that turns the pump off when there's a problem (no water, no exit, whatever) but has no "off" button. Power from an earth leakage detecting power strip in the garage for a bit of safety. Cheap way of joining tanks. 25mm pipe and silicon sealant, but because this is the bottom of the tanks any failure means both tanks empty. If I can get cheap tank outlets I'll probably replace this. The big tank. The clear hose on the right also lets us see how much water is in the tank, and the valves on the Y connector are much easier to turn than the big one. I'm a little worried that the wiggling that the big value does when I turn it on will weaken the tank. Cheap tank joiner two: 90mm pipe at the top of the tank. Relies on the holes being at exactly the same height and makes the tanks hard to move. But if it leaks it really doesn't matter too much as most of the overflow from the first tank will still go into the second one. The inlet filter on the left hand tank is not needed but the hole is there and until I make a cap to replace it the filter is better than an open tank. Looking through the joining pipe at the overflow in the main tank. Other side of the linking pipe showing that the first tank is full enough to start filling the second one. The overflow in the first tank is at the same height as the joining pipe because the top of the hole is right at the top of the drum. This blocking thing means the tank doesn't overflow to stormwater until both drums are really, really full. Some of our garden bins - polystyrene containers from the local greengrocer. I also bought an inline diverter which we're using on the second kitchen because a drum would block the doorway. Also I couldn't get the downpipe out because it's rivetted and silicon sealed into one piece. So I cut 30cm out of the middle and put this in. The plastic bottle stops splash going everywhere when drips come down the pipe and hit the diverter. In place. The top bucket is tilted slightly so that it overflows into the one on the ground. We also have a roofed area that has no guttering and so is slowly rotting away. These buckets catch some of the flow from that roof. At the top you can just see where I used the cut-off from the downpipe to guide more flow into the big blue basin. Closer view of the "funnel" Garden with apricot tree on the left. The closest section we dug through and sifted to about 30cm down, getting an astonishing collection of rusty nails, stones and assorted junk. I think they either burned rubbish there or just dumped the ash from an incinerator or barbeque there. Icky either way. Phuong planting out the front garden/lawn area. Phuong hunting caterpillers.
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