Building a rain water tank

[diy_woodie]

Hi,Water is a precious resource and I would like to collect rainwater from our roof. (I'm doing a raingarden in the front yard - http://wsud.melbournewater.com.au/content/treatment_measures/treatment_measures.asp ).

I don't water the garden apart from a few buckets of bath water so rainwater is best used in the toilet and laundry.I'd like to build a rainwater tank that could basically go along the fence line. I have a 10 metre long back yard with a small planted section on one side which I thought would be good to retrofit a tank into. So it would be about 1.4 metre high, 0.5 metres wide and say 9 metres long - giving a capacity of about 6000 litres. Then it is plumbed into side of house where laundry / toilet is.

The slimline tanks are quite expensive so figured if there was an option to use 18 mm ply as sides and a concrete base it would work out a bit cheaper and would be custom fitted into the space I want. Obviously needs a very good seal !

Is plywood water proof? Is this a stupid idea? Time is not a problem - I'll work on it over winter so it might take 6 months but will be worth it in the long run. Wonder whether I'd get a rebate for that kind of tank too ?ThanksRob

[silentC]

I guess you could make the ply waterproof - they make boats out of it. Don't know how long it would last though. Wooden boats need constant maintenance to protect the timber. You could paint the inside with Silasec and cement.

Even better, use the ply for formwork and pour a concrete tank.

[SilentButDeadly]

Marine ply will work but it only comes in 2.4m x 1.2m sheets and you'll be dead lucky to play less than $180 for a 17mm thick sheet. Adding the cost of the galvanised steel or timber structural frame you'll need to hold the lot up and the Sikaflex you'll need to seal between the sheet joins means that a tank of this size won't come cheap...

If thee were me and you wanted a custom tank then I'd look to gal steel posts every metre or so with at least 600mm into the ground and concreted. Screw sheets of corrugated iron to the inside of the posts. The base needs only be screed sand. Line the whole construction with pond liner. http://www.rockaroundtheblock.com.au/categories.asp?cID=35&c=173521 To make the thing really strong brace the poles across the tank to stop them being pushed outwards.....cover the tank with sleepers or more corrugated iron.

[rat52]

You would need to use a liner similar to above ground swimming pools

[varpy]

You could find yourself in deep pooh if the thing collapses. Absolutely nothing worse than a failed DIY that turns into a catastrophe.

Mind you I've just resurrected and old gal tank. Round ,about 800 mm diameter and 1.8m high. The bottom was rotten and someone had taken to it with an axe so a 75 mm reo concrete base with added silasec and a few pop rivets then painted with Gripset 51 and it is a go-er!

Gripset should be considered in whatever you do. God awful to apply but it is a waterbased biyumen/rubber compound. Cheaper than a liner, but not as robust.

:)