If you live in or near the coast line or in a high water table area including the gulf region of the U.S., Florida, Louisiana and other water retaining areas then you need to read this.
What is hydrostatic pressure?
Hydrostatic pressure is a hydraulic force caused by the build up of underground water pressure that can cause your swimming pool to pop out of the ground. A swimming pool filled with water creates enough counter pressure to offset the hydrostatic pressure pushing up under your pool so you are likely to discover the problem after you drain your pool. An empty pool does not have enough counter resistance or shear water weight to keep the pool in the ground. To understand the concept of how powerful water can become, think of a massive ship at sea being tossed around by the mere displacement of water. The hydrostatic pressure can sometimes lift just a part of the pool causing severe structural cracking and damage and other times pop the entire structure up enough to release the pressure.
If you think this pool problem is rare and probably will not affect you, think again! If you are about to build a new swimming pool, remodel an existing one or are about to draining your existing pool and you live in or near the coast line or in a high water table area including the gulf region of the U.S., Florida, Louisiana and other water retaining areas then this for you. A single pop up can render the investment into your pool worthless and cause you to spend many more tens of thousands of dollars trying to repair damages. In many cases making repairs is futile or cost prohibitive making the only solution to demolish the pool and start over again.
If you have been shopping for a swimming pool contractor you might have noticed that there is a pop-up or lifting clause written into the fine print of the contract that either specifically voids the warranty or waives the contractor's liability when the pop-up occurs. Voiding the warranty or not covering damages caused by the pool pop up is considered normal practice in the pool industry.
If you are remodeling your pool please do your research BEFORE draining your pool. If you are building a new pool, please consider installing a Hydrostatic Relieve Valve and Collection Tube to help prevent possible lifting. The valve is designed to release the pressure into the pool rather than allowing the pressure to build up under the structure. You should also consider placing a gravel rock pack around the collection tube to prevent the soil from clogging the tube. For the best results, you might want to consider placing gravel rock across a large area of the pool in both the deep and shallow ends to the water can more easily find its way to the Hydrostatic Relief Valve.