Occasionally a client contacts us wanting to build a pool in an area with a high water table. This typically happens in low-lying areas and along the shore. Hydrostatic pressure is the term for the force that water exerts upon other objects when it is not in motion. This happens when water within a pool exerts hydrostatic pressure on the walls and floor of the pool from the inside. Groundwater also exerts hydrostatic pressure against the walls and floor of a pool from the outside.
The pool above belongs to clients that came to us years ago wanting to build a pool in their backyard. The back of their property was quite wet, and with a high water table. These clients were concerned it might be problematic to locate a pool in that location.
If your pool is adjacent to a large body of water say a lake, the bay, or lagoon, then it may be affected by hydrostatic pressure. If this is the case, extra precautions may be required. First, you need to determine how high the water table is and this can usually be done with a water table test which consists of drilling a hole to a depth of 3 meters, allowing the water to stabilize, then measuring the distance from the groundwater to the water level.
This stone retaining wall doubles as a coping and wraps around to the inside of the pool making tile unnecessary
In certain cases, if the water table is exceptionally high, then it’s a good idea to bring in an engineer. In extreme situations, the engineer may specify anchoring the pool into the ground. This can be done in various ways and although it sounds expensive, it’s a fairly straightforward process that shouldn’t put an undue strain on the project budget.
Another solution can be to raise the elevation of the pool to a level where the hydrostatic pressure is less of an issue. The goal here is to simply raise the pool vertically, creating distance between the ground water and your pool. If we come in contact with ground water while digging, we simply continuously pump out enough water to keep the hole dry enough for digging.
Once the pool is installed, we keep the pump running until we can get water inside the shell. At that point, the pressure from groundwater and the pressure from water within the pool essentially cancel each other out. The rest is easy.
We raised the elevation of this pool a few feet above existing grade and created a series of terraces supported by low stone retaining walls.