# Forum Home Renovation Water Saving Garden Ideas  what size rain water tank should I get?

## breakerboy2000

Hello, I am hoping someone can do the calculating to determine which size I should get, 
so firstly, it is only going to be collecting just from my shed roof ( 3 x 6m with a slight A frame roof) 
I want to install a sink there, so I will not be using much, only when I am in the shed, for cleaning tools, washing hands etc.. 
I am not in the shed everyday, maybe 2-3 days a week..  
I am on the gold coast with around 1300mm of rainfall a year 
Would a 200L tank be enough? 
thank you

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## Farmer Geoff

If a year's rain was piled on your roof, at 1.3m deep over 3 by 6 metres that would be 23.4 cubic metres which is 23,400 litres.  Problem to contemplate is the timing of the rainfall. If you go 6 months without getting any then you either need to store enough to supply your demands for 6 months or else you can decide to use town water for that period, either directly in your shed or else to part fill your tank.  Take a guess at your usage and go from there. eg you might use 20 litres per day you are in the shed. So that's 60 litres a week which is 1,560 in six months. At that rate you could get by with a 1,500 litre tank, less if rainfall was spread throughout the year, more if you use more than 20 litres a day. If you don't need pressure or don't want to buy a pump as well then you might need a squat tank on a stand or else a bigger tank since you might be only able to use water in the top half of the tank. A 200 litre tank is very small - you could easily make a stand for it to sit on. If you use such a small tank, you might only need to catch water from one side of your roof, thus saving on guttering and pipework. It will overflow often so include a plan to handle that. Check local council website to make sure you comply with their regs. Good luck

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## breakerboy2000

Thanks for that detailed response farmer geoff, 
I dont see myself using it alot, its just going to be there for the convenience, rather than having to go up to the house to fetch water if I need it, i was thinking of grabbing some 44 gallon plastic food drums and adapting them to tanks, maybe 2-3 should be enough?  I am wanting to build some kind of stand for them, above the outlet tap and underneath the guttering collection and let gravity to the work rather than using a pump.

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## Batpig

Dear Breakerboy, 
Try this website: Tankulator - Home page 
For the task at hand, it truly kicks R's... 
Best Wishes,
Batpig.

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## johnc

I used a 200 litre tank for years off a similar sized roof for much the same purpose and never ran out of water, that was with annual rainfall of about 600mm. If the holding capacity (the tank) is free why not just start with one and see how it goes. We now use a 3000l tank and it also gets used on the garden, it does get drained in summer.

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## SilentButDeadly

Just a hint...if you don't plan to drink from it and (in the interests of recycling) you might want to consider acquiring a used intermediate bulk container.  They hold about 1,000 litres and can typically be had for around $150 though that is dependent on demand where you are...I got a B grade used one for $50 and there were plenty to chose from

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## David.Elliott

taking the overflow from our tank...
I have mine in the shade/undercover. The challenge is that as they are translucent algae will grow in them due to the light. Still empty them each summer on the garden...

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