How can I tell if my pool is no longer level?
Tuesday, May 7, 2019
A new in-ground pool is level or very close to it. But, as the pool ages, a small amount of settlement is normal and a pool that is several years old and 1/2” to 3/4” out-of-level is not unusual. Once the difference is more than 1” you are in the range where it will begin to cause problems. Although the shell of the pool may not show any cracks initially, there are multiple right-angle pipe connections underground that will be stressed and likely to crack and leak. This leakage can lead to more settlement. Also, damage to the coping is typical.
The distance between the water level in your pool to the top of the tile line or coping will be the same all around a level pool. Checking your pool this way is a quick and simple process.
The fiberglass pool shown below is one where it was easily visible that the pool was sinking at the deep end, even before measuring. A heaving deck above the middle of the pool was further evidence of a problem.
Measurements taken at both ends of the pool showed a 2-1/2” difference from top of coping to water level.
Further inspection around the perimeter uncovered a likely reason for the settlement problem: the lot sloped away from the pool at the back and loose rip-rap rock appears to have been initially installed to keep the angle of repose of the soil in place. But, when soil washed through cracks in the rock, concrete was poured between them (see arrow), which also loosened and allowed continued soil movement down the slope. This problem, which is called “slope creep," will be difficult and expensive to repair, and a retaining wall built as part of the pool installation would have avoided it.
Other defects that can cause settlement include inadequate compaction of the soil, poor quality soil with organic debris in it, and expansive clay soil. An unusually high water table during a period of heavy rain can also cause a pool to shift upward, although a hydrostatic relief valve in the bottom of the pool can mitigate that issue.
If you are lucky enough to have an “infinity edge” pool, with water spilling over one edge into a trough so that it merges seamlessly into the horizon beyond, then no measurement is necessary if your pool is settling out of level. The water will begin flowing over only part of the edge.
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