inground swimming pool inquiry 1

[civilsid]

I am in NW Arizona and remember working for an engineer several years ago and we got a few calls from home owners that had inground swimming pools begin to float on them, obviously from the build up of hydrostatic pressure. I have never heard of this happening back east (western NY) where the water table is only a couple feet down and they get lots more rain.

Is this only a potential problem if the pool is empty, i.e. no equivalent water weight on the inside to hold it down?

Is this a rare occurence or are there reasonably prudent measures that should always be taken to prevent this?

I am thinking maybe in my area, they may not take appropriate precautions since the rainfall is minimal and the depth to the water table is hundreds of feet.

Any insight would be appreciated.

 

[jike]

It has alot to do with soil conditions and water table, but I believe it is always prudent to check for buoyancy so it cannot pop out of the ground.

If you have all granular material and a low water table, it is unlikely that you can raise the water table significantly, unless you are in a low land or next to a river or lake.

You may create a perched (water table)condition if you excavate in clay and backfill with sand. Rainwater then can saturate your sand backfill but it would be unable to disapate because of the clay. Essentially, you will be building a swimming pool inside of a swimming pool.

Providing a sloped clay cap would help force the runoff away rather than accumulating in the excavation.

As you can see, there are many considerations so there is no simple answer.

 

[epr]

It is actually a very common problem in many areas.
The easiest thing to do is to maintain a reasonable amount of water in the pool (in addition to the concrete weight)to counter the buoyancy.

Additionally, since there will undoubtedly be times when the pool must be emptied for maintenance, the bottom should be constructed with hydrostatic relief valves fitted to collection tubes. Any gunite pool manufacturer can assist you with this product.

 

[oldestguy]

Watch out for maintenance guys deactivating check valves, in hopes of reducing water loss thu a partly closed valve.

Then when they wish to dewater, the valve is not functioning and adjacent high ground water does its thing any place, including NY.

 

[civilperson]

If the pool structure is designed for neutral buoyancy then it will never float. This how box culverts are designed in Louisiana. Keep thickening the walls and bottom to achieve an empty weight equal to the weight of the same volume of water, (volume of external dimensions).