Under the Choko Tree By Nevin Sweeney

Water Harvesting and Storage

Over 30 years ago, back before it was common to have watertanks in the suburbs, I wanted to have our own independent, sustainable (although the word wasn’t used much back then) water supply and rainwater was the obvious way to do it. We had just put a hardiplank garage on the side of the house, the stormwater drains were all uphill from the downpipe and the builder said I should put in a rubble drain. Problem was it would have destroyed my main veggie patch, so I asked the council inspector about water tanks instead and after a bit of thought he said OK.

Galvanised 500 gal tanks

I wanted the old country style galvanised corrugated iron tank so we got a 500gal tall form one. It looked great and  I was happy with it, but how to install it? I went to our local timber yard and they told me how –
First dig two trenches 4 foot apart, four foot long by one house brick wide. Lay house bricks in the trench side by side and cover them with concrete, this made a really good footing. Then lay three courses of bricks on the footings so that I had two brick “walls” four feet apart and parallel with each other and I let the concrete cure for a week. I am no expert brickie but so far so good.

Then I bought timber for the platform to support the tank itself, I bought 75mm x 100mm joists to go between the two brick supporting walls with about 300mm between them. I then nailed 150mm x 20mm hardwood over the joists to form a very stable platform on which the tank was to sit. The tank was installed, connected by just cutting off the downpipe to the right height and angling it towards the tank filling point. I t filled up rapidly, so rapidly I decided I wanted another. I followed the same process to the right of the original so that both tank stands flanked the garage back window, but the second one only had two courses of bricks so that I could run the output pipe from the first tank directly into the filling point of the second.

When we bought the second tank we were given a plastic strip with a mystery chemical in it (I think it may have been a phosphate of some type), it was to be suspended in the tank and the water would dissolve it coating the inside of the tank, reacting with it and extending its life. I had people tell me that the life of a galvanised water tank in the city was about 5 years, but the original one lasted about 15, sprung multiple leaks and died. We replaced it with an Aquaplate, plastic lined one and it is still going strong, as is the second one. There was only about 6 months between the first and second so that chemical worked! Mind you, by the time we replaced the older tank, water tanks were becoming popular again, so the bloke who sold it to us said, and he could charge more for them!

The tank stands are still in place, although the wood bits are looking a bit worse for wear and will eventually require replacement, but the service life has been pretty good!

5500 litre plastic tank

About 3 years ago, with the government rebate and all we decided to increase our water storage from 5000 litres to over 10,000 litres by adding a green plastic 5,500 litre tank to the front yard. While I prefer the look of the old galvanised corrugated iron, the plastic tank gave us the best cost per litre of water storage and it is installed under the mulberyy tree, so even though they are UV stabilised, it should extend its service life even more. There is no way I was going to try the same trick with the bricks and hardwood to support it, so I was thinking about getting one of the guys from work to help me putting down a slab.

The guy who delivered the tank suggested another way – get treated sleepers and make a square two  sleepers high a bit bigger than the circumference of the tank, then shovel in a whole stack of small size blue metal gravel and fines, the larger pointy stuff can wear a hole in the bottom of a plastic tank over time. So that’s what I did, setting it up next to the roof outlet. It works remarkably well. I had to butcher the downpipe because I couldn’t line it up properly with the top of the tank, but I could still channel overflow from the tank back into the stormwater.  Mind you, you can be feeling pretty good about yourself but you can’t fool a shovel and a couple of tonnes of gravel!

The green tank takes water from about 1/3 to ½ of the roof, and the two galvanised tanks take all the water from the garage roof, but when I had the 30 year old guttering replaced recently I was able to get an extra downpipe put in from the house gutter to the garage roof so that I could capture more water. The new downpipe has a valve on it so I can turn it off in the event of wet weather when the galvanised tanks are full.

Extra downpipe to garage roof with valve

So we now have over 10,000 litres of water storage that gets used around the house, but our strategies for how we use it  will be covered off in another article.

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