Underground Rainwater Tank

Hi All,

Up to the stormwater stage of planning... And, of course, Basix...

Wondering about rainwater tanks... For an underground tank, are there advantages with concrete tanks vs poly tanks?

What about differences in prices... And anyone willing to pass on some general costs for tanks, accessories, digging a hole in the ground etc, etc...

What about placement... Any problems underneath driveway? By the way, our block is fairly flat, and there is only a 100-200mm fall to kerb...

Any advise/input would be much appreciated...

Cheers...

morning! we enquired about under-driveway tanks - pretty pricey.

From memory (1.5 yrs ago was when we were looking) - for a 5000L system, we were quoted about $7k for the tank.

For a non-load bearing system like the Bushmans underground tank (e.g. under garden beds or lawns) - I think it was about $5k for the tank. But around another $5-6k for installation - digging the hole etc.

These tanks were all poly - never thought to ask about concrete ones.

Our builder charge us $7500 for above ground, with option of extra $5000 to go underground. We didn't take it as it's too expensive...

An absolute ripoff at that price for an above ground tank.

We got some quotes for underground concrete tanks just recently from brisbane

Our prices to supply and deliver only. GST Inclusive.
1 x 32500 Litre Concrete Rainwater Tank $4383.50
1 x 22500 Litre Concrete Rainwater Tank $3228.50
1 x 10000 Litre Concrete Rainwater Tank $2623.50
1 x 5000 Litre Concrete Rainwater Tank $2183.50

EXTRA COSTS IF REQUIRED.
Installation Cost (Brisbane and Gold Coast Areas) $1870.00
1 x 22500 Litre Heavy Duty Lid $1342.00
1 x 10000 Litre Heavy Duty Lid $ 902.00
1 x 300mm H x 600mm Dia Necks for H/D Lids $ 297.00
1 x Gatic Lids for Necks $ 506.00
1 x Onga 75/35 Submersible Pumps $660.00

We liked the idea of getting 22500l tank with heavy duty lid so it can be placed under the driveway. I thought it was expensive but with all the prices everyone has been saying for above grounds these are quite a good price.

That's pretty reasonable.

If you had 22,500L of storage - you might even be able to avoid being connected to the mains water - besides sewer requirements.

stonecutter1309,

I doubt that it would be enough unless they are really water misers. Average household in OZ uses around 350 000L per year. A 22 500L tank would have to refill around 15 times per year to provide this.

Most people I know with 100 000L tanks still need them refilled from time to time and some even install a second 100 000L tank to cover them.

If your rainfall is high enough though (maybe FNQ) then you may just get away with it but I doubt it.

I think you should target certain areas eg toilets and washing machine or garden etc.

3xb - I was thinking of the Michael Mobbs place - I'm fairly sure his tank was relatively small. In any case - their house is run on 100,000L per year from rainwater.

Blackwater is recycled on site in to grey water and used for toilet flushing and washing machine.

Grey water is also recycled on site and used for toilet flushing & washing machine.

I was just thinking the 22500L would be great for toilets and the garden. Yeah I dont think there would be enough water to run everything though unless you get many large rain events.

Hmm that may be a little largish??

Have you heard about "Smerf"? They sell a underground water tank that is the same size as the waffle pod. Don't know how much it cost, but could be another option for you.

I got some information on my blog here:
http://building-our-first-house.blogspot.com/2007/08/others011-smef-water-storage-innovation.html[/url]

I came across these and they certainly look intresting. Anyone used them before? Comments? They sound good but I am just not sure yet, I like the idea of flexibility with shape and size. Thinking of putting them under some decking, so strength is not really required.

http://www.undergroundwaterstorage.com.au/index.html

Sounds interesting - I wonder what the cost is?

I've dropped them an email asking for a rrough guide so will see what they come back with.

FYI

I have 2 13 000L water tanks that provide all our water requirements. We have being in our house for nearly 1 year, only once did we have to switch back to town water.

For someone to run out of water from a 100 000L tank, they must have a high water usage!

Well looks like it is out of my price range:

An indicative price of a 40,000L tank fully installed...
Includes: excavation, spoil removal, modules, liner, geotextile, sand,
filter and pump.....
$ 29,500

Oh well, keep looking.

Holy crap!

My sentiments exactly. Cross of a zero perhaps.

I find it amazing that these new plastic tanks are often more expensive than building a huge concrete one!

I really thought it would be a cheaper option. Perhaps it doesn't scale up well, a 1000L Tank from them might be $2000 which for somethng you can drive over is not too bad I guess.

Any links to underground concrete tanks?