# Forum Home Renovation Concreting  Concrete slab for water tank

## tourgy

Hi everyone,
I have purchased a 4500 litre plastic water tank that will be delivered early April. Got a good deal so it was too good to refuse :Biggrin:   
The people I purchased it from recommend putting it on a bed of riversand.
I want to put it a bit higher and when I told then I was thinking about putting it on house bricks the did not recommend that as some of the bricks may crack. 
My other option is a concrete slab which I am awaiting a second quote for (the first quote was very high and scared me). 2 metred squared at $700. 
Another option I was thinking of was the thick concrete square pavers you see around the place and doubling them up so there is a bit of clearance for the bottom of the tank. 
What is the general consensus on these? Will they be ok to hold the weight without a problem or should I get a slab layed down? 
Oh and please do not recommend I do the work myself as I have stated in earlier posts I am hopeless when it comes to doing this sort of stuff  :Blush7:  . 
Not good I know. But at least I can make excellent beer. So I reckon that counts for something. 
cheers
tourgy

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## floobyduster

Hi tourgy 
If you make great beer and have a few mates the answer is obvious - just have a working bee for free beer  :Smilie:   
Assuming you only want it a little bit above ground level, all you need to do is peg out some boxing nice and level, screed down a sand base, drop in a bit of mesh, pour in concrete and screed off to top of boxing. Then, just sit back with that nice cold beer  :Biggrin:

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## DavidG

1. Why do you want it a bit higher?
2. Have you thought about using treated pine sleepers.

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## rick_rine

with my plastic water tank when I pumped up from the creek it caused minor vibrations in the tank . For this reason I would stick to sand as maybe the vibrations against the concrete may cause friction and rubbing on the plastic eventually leading to weakening the tank .
My 2 cents worth 
Rick

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## silentC

Whatever you do, keep in mind that when full that tank will weigh over 4 1/2 tonnes. 
Haven't had much experience with plastic tanks but with steel tanks, it's important that whatever they are on is flat with no undulations as it can cause the bottom seam to split. Probably one reason they recommend river sand is that it will conform to the bottom of the tank and support it evenly. I'm not sure I'd like to sit 4 1/2 tonnes of water on a base of pavers or bricks unless it was very stable.

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## Bleedin Thumb

No- probably the same reason those above ground swimming pools are set on a thick layer of sand.
And once again what is the advantage of raising it 100mm when the tank I guess will sit what 1.8m high?

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## tourgy

Thanks for the replies all. 
The only reason I wanted it raised a bit was so that when the hole for the outlet gets drilled it is as close to the bottom as possible.
I'm not even sure if I am making sense here so bear with me. 
If I dug out all the loose earth in a 2 sq mt area till I hit the clay it would cause the bottom part of the tank to be a few inches below the rest of the ground around it. Unless if course i filled up the 2 sq mt boxed area with sand and brought it back to the level of the ground around it. Which come to think of it is what I am probably supposed to do.  :Doh:  
I can see where the recommendation of sand is coming into play. The only problem i have with that is that I still need a solid base to mount the pump on. Hence the original thoughts of the slab being layed. Plus if the tank is at the same level as the ground around it, how low can the outlet hole be drilled in? 
What about those concrete paver type slabs? Would they be stong enough? Safety is of the most uppermost importance as well due to kids running around the back yard etc.  
cheers
tourgy

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## silentC

Plastic tanks usually have the outlet pre-formed in the side of the tank, so you probably wont have control over the height. They're usually an inch or two from the bottom so that any crap that collects in the bottom of the tank doesn't block it up. 
If you are fitting a pump, the height shouldn't make any difference...

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## Felder

> The only reason I wanted it raised a bit was so that when the hole for the outlet gets drilled it is as close to the bottom as possible.

  Tourgy, 
DON'T make the mistake I made when I drilled a hole in my tank! I drilled it as low as I could, figuring that this would give me the maximum use of the water I collected. 
Right now, I can hear all the bushies just shaking their head.....bet you blokes know what's coming up...... :Redface:  
The hole I drilled was too close to the floor of the tank, meaning that the inside flange of the outlet pipe was hitting the floor, and not allowing the outlet pipe to poke through the hole squarely.  :Doh:  :Doh:  :Doh:  
There was a very loud, very echo-ey curse word that emitted from the top of my tank when I found out what I had done, followed by much patching, painting, etc.

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## Barry_White

When I was with Lysaghts the tank manufacturers that I called on used to make what is called an earth ring which was just a ring made from tank iron which was just 200mm larger in diameter than the tank and then this was put on the ground and filled with sand and then the tank just sat on the sand. 
You could do this with some treated pine sleepers and build it like a square retaining wall and fill it with sand and sit your tank on that. 
The other method would be to make a tank stand out of steel purlins. 
If I can find the design I will post it for that size tank.

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## ausdesign

We just installed about the same size on ground that had a reasonable slope. 
rather than digging in & greating drainage troubles we built the ground up with t/pine perimeter & then compacted packing sand. - possibly looks a bit unsightly until the plants grow [round tank. square base]

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## ausdesign

There's an echo in here . . . I like the steel ring idea bazza :2thumbsup:

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## Buzzer

Tourgy,
What Felder said, also I would leave 2 to 3 inches of water in the bottom of the tank so it wont blow away in a storm. 
My experience with putting sand as a base is the little digging critters find it easy digging, get under there and dig the sand out and make a home, leaving voids under the base. 
I have levelled the natural earth(it has no rocks) under 3 poly tanks(7000 gallons each,for stock water) and so far haven't had any problems. They have been there about 5 years. 
Of all the tanks I have seen around here, none have concrete pavers under them so I don't know how successful that would be. 
Cheers
Buzzer :Smilie:

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## MICKYG

Tourgy, 
We installed 10,000 litre which is on a crusher dust base, a circle of about 3 metres. The outlet pipe is about 100mm above the base, you do not want silt coming out of the tap every time you turn it on. Its been in two years now and never been below 1/2 full and is used to water the Vegie garden and beautiful cool drinking water for our houshold. We also installed a pre tank filter which dumps the first 50 litres off the roof. 
Regards Mike. :Wink:

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## Barry_White

> There's an echo in here . . . I like the steel ring idea bazza

  They need to be made from Aquaplate to prevent corrosion on the inside of the earth ring.

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## DavidG

DO NOT FORGET that the line from the tank to the pump must be flexible or you will split the tank at the outlet flange.  :Shock:

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## tourgy

Hi everyone,
Thanks for all the help so far. I think I will drop the idea of a concrete base and go with the manufacturers recommendation of the sand base. 
Seems to be the norm from what you have all said. Makes sense about the sand allowing the bottom of the tank to mould itself into the sand. 
My only problem now is what to mount the pump on. There is nothing but earth where the tank will be installed so I am not sure what to do about this.  I could put it around the corner but that will make it 3-4 metres away from the tank.
Would this have any effect on the pumping power? Or does it make no difference what the distance of the pumpp is from the tank? 
Cheers
tourgy

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## silentC

You can buy small pre-cast slabs about 400mm square and a couple of inches thick at hardware or building supplies.

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## Bleedin Thumb

> but that will make it 3-4 metres away from the tank.
> Would this have any effect on the pumping power? Or does it make no difference what the distance of the pump is from the tank? 
> Cheers
> tourgy

  Very little unless the feed pipes daimeter is so small that the friction caused by 3-4m of line reduces flow - very unlikely, given the pump is being fed with positive pressure from the tank. It would be a different situation if the pump was above the water source. 
Assuming the pump will still be sitting on the same level as if it were beside the tank you should get the same amount of head from it.

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## Buzza

Depending on how high you need to go, which is governed by the top of the tank in relation to your roof guttering, you could look into one of thos ready made concrete culverts. Check out your local pre-stressed concrete people. These things are shape like a square U and placed upside down. They act like a table for your tank, and the underneath area can be used for a doghouse, or firewood box etc: 
If you use sand, it must be gently watered in then "critters" will have little effect. You might want to put a membrane between the sand and the tank as well. In the old galv days, we used tar-paper. :2thumbsup:

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## echnidna

screw the pump down to a short piece of sleeper and just let it all sit on the ground

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## kayep

All interesting stuff, but what does the manufacturer of the tank you have bought recommend? 
I have seen other manufacturer (Clark Tanks) recommend the following 
1. Ensure the location of the tank is level, stable ground which has uniform compaction (free of soft spots). Do not locate large water tanks close to retaining walls or embankments without first consulting a professional engineer to ensure the ground is capable of supporting the weight of the full tank. *2.* Ensure the surface of the site is free from sharp objects or stones and is compacted. *3.* Spread a thin layer (approx. 20-40mm) of 3mm metal/crusher dust  bedding sand can be used but is prone to erosion  evenly over the level ground, at least 500mm more than the diameter of the tank. Once it is compacted and level you may then place the tank directly on top of this material. To assist with reducing soil erosion, back fill to first rib. *4.* Ensure the metal/crusher dust is contained under the tank at all times and cannot be washed away. This can be achieved by diverting all run-off water away from the site and retaining the metal/crusher dust with some form of retaining structure e.g. cement strip, rocks or sleepers.

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## Ian Smith

Tourgy,
The last thing I'd claim is to be is an expert on water tanks, but with the way this drought is going I think we'll all be a little wiser in the near future.
I've just installed a 5000 litre poly tank on a cracker dust base and I think that's the way to go. 
I think if you use concrete it needs to reinforced because if and when it does crack the pieces don't move relative to one another in the vertical direction. I reckon the same would go for pavers etc, I think that if there is vertical movement you'd get a shearing force applied to the base of the tank and I'm guessing it could tear.
Anyway the cracker dust is cheap and easy to put down.
Here's a couple of pics which may be of some assistance 
Ian

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## tourgy

Thanks for all the help so far. 
Like I mentioned earlier i will go with the manufacturers recommendation of a bed of river sand. But I do like the look of what Ian Smith has done. 
Ian, Has that cracker dust been compacted with something? Or did you just lay it down and level it out before putting the tank on it. 
I was going to make a border of house bricks, But may use something like what Ian has done as they are a bit larger and basically gets about the height I wanted off the ground. What are those concrete looking bricks called? 
As far as where the tank will be located it will be at the back of the house as this is about the only lcation I have where it will collect a good amount of water. I Intend to put it about 30-50 cms away from the main wall. It will be rather unsightly. I can post a picture later.
This wont be a problem will it? As far as I can tell the earth around here is clay and very very hard. I tried to dig a small hole out the front once and gave up it was so hard. 
The company is http://www.waterstore.com.au/index.asp and the price of the 4500 litre tank was $895 delivered with some fittings supplied. 
Bit nervous of the location now because yes, when full it will be very heavy. 
Cheers
Tourgy

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## Doughboy

Tourgy those large looking brick thingys are called Besser blocks. The crusher dust would need to be compacted with a plate compacter. If you dont the middle will sink and damage your tank. Proximity to the house is not an issue, you HAVE to make sure the tank has a level base to sit on. 
If you consider a tank to be unsightly then just put a sheet of mesh around the 'visible' side and grow a passionfruit vine or a climbing rose or a potato vine or a star jasmine vine over it. One of these will have it covered in no time. 
Pete

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## Ian Smith

Tourgy,
Yep, zackery wot Doughboy sez 
Ian

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## tourgy

Thanks for the clarification on those bricks Doughboy and Ian. 
As I dont have access to a compactor I may just go with the sand. Reading the instructions from the manufacturer they recomend a border of some sort of bricks then the sand. It does not mention anything about compacting it.  
But they recommend the border of bricks after the tank is in its resting spot. Basically says build a level of sand 50-100 mm high, put the tank on, then border it with bricks. 
Cheers
Tourgy

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## journeyman Mick

tourgy,
without a compactor your best bet would be to build a border and use fine sharp sand (plasterer's sand is ideal) and water it in. This will compact it. Don't use river sand as it's usually coarse and rounded and will not compact. 
Mick

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## silentC

> I dont have access to a compactor

  Just about any plant hire place will have them for hire. As you're in Melbourne, I'm guessing there's a Kennards or similar in a suburb near you!

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## Bleedin Thumb

> tourgy,
> without a compactor your best bet would be to build a border and use fine sharp sand (plasterer's sand is ideal) and water it in. This will compact it. Don't use river sand as it's usually coarse and rounded and will not compact. 
> Mick

  
That shows up the problem with local names for different products - sands in particular. 
In Sydney River Sand - especially course washed river sand is used for paving bedding and is very compactable. 
Beach Sand on the other hand is not compactable being fine, which is different to Perth I think? 
Its all to do with the *G*ap *G*radient *P*article *S*ize but you all know that, don't you.

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## hatemondays

Tourgy
you did very well to purchase your tank from waterstore. They would have to be one of the most professional organisations I've had the pleasure of dealing with. I actually rang them after I got their tank siting instructions and asked if it was ok to place tank on concrete rather than sand. Their man told me no worries at all. Tank been in for 5 weeks now and filled it to capcity just last night 
Concrete pad I laid still showing no signs of cracking under weight. :Smilie:

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