Installing 2500gal above ground tank. Do I need a concrete pad?

[TXTom]

I am getting ready to add a 2500 gallon storage tank to my water system. I am using a 2500 gallon polyethylene tank. the tank will be sitting at ground level. I would prefer to scratch out a nice level spot and then compact 3-4"s of base or filings for a pad. The soil in my area is a combination of black dirt and perforated limestone. Solid rock is more than 2' below grade. What are your experiences with installing storage tanks on grade?

Thanks,
Tom

 

[Rancher]

I have a 3,000 gallon poly tank on a bed of pea gravel, no problems. I have two 5,000 gallon poly tanks on dirt, no problems.

Rancher

 

[Sponsor]

 

[Bob NH]

When installing tanks on grade you should remove the organic topsoil and put down a sand or gravel base. It is best to use a coarse, sharp sand and even a little stone up to 3/4" mixed in is not bad. If you have good well drained soil you probably don't need additional sand. Beach sand is not good because it has rounded grains and tends to displace under load.

If the sand comes above surrounding ground then you need some kind of confinement to keep it from washing away.

There should be means for the water to drain away since any standing water weakens the soil and the tank will sink into the mud.

The load is about 500 to 600 pounds per square foot when it is full of water and it takes quite a structure and foundation if you are going to put it on any kind of deck. I saw a 4000 gallon tank that someone had put on a deck made of pressure treated material and the foundation was so inadequate that it settled unevenly and distorted the tank. I have also seen tanks on the ground where the topsoil was not removed and they also settled unevenly. The tanks tilted and the walls buckled in areas near the bottom.

 

[hj]

tank

The load is about 500 to 600 pounds per square foot when it is full of water

That depends on the design of the tank, a tall slim one will have a higher force factor than a short wide one.

 

[Bob NH]

The load is about 500 to 600 pounds per square foot when it is full of water

That depends on the design of the tank, a tall slim one will have a higher force factor than a short wide one.

62.4 pounds pre square foot per foot of height of the water. Good compacted soil will handle 2000 pounds per sqaure foot, and many will handle more than that.

A few inches of unreinforced concrete is going to crack badly, and a deck nailed to a few pressure treated timbers is worse than plain sand or gravel on undisturbed mineral soil.

 

[Gary Slusser]

PE tanks can't take sitting on sharp edged or pointy thingies without eventually poking a hole through them. So check with the manufacturer or their dealer for more info on the base and its material you intend to use.

Then you need to start thinking of the water quality degradation in the tank and what you'll eventually have to do to prevent it or improve it before use. I think there is another thread here where that is dealt with, you might want to look it up.

What are you going to use this water for and why do you need this cistern/tank to begin with?