- Recurring deposits of sand in a pool often signal filter failure.an open swimming-pool image by Valeri Vlassov from Fotolia.com
Maintaining a pool is hard enough, without having to deal with sand mysteriously appearing on the bottom of your pool, shortly after you vacuum it. Because most pools use a sand-based filtration system (unless your system uses diatomaceous earth), sand can accumulate in the deep parts of a pool, when filters are operating incorrectly. A punctured liner also can cause sand to leak into the pool, and you cannot forget environmental causes of a sandy pool, such as carrying sand in on your feet. - All types of sand filters operate in the same general fashion, pushing pool water through a tank filled with sand, upon which oils and other pollutants accumulate. When water reaches the bottom of the filter, it is reclaimed through pipefittings, known as laterals, which are designed with openings small enough to keep grains of sand from entering. When backwashing the pool, water flows in the reverse direction, from the laterals, to the top of the filter, cleaning out residual pollutants off the sand. Pool Wizard, at Havuz.org, recommends you change your pool sand every three to five years, or you will get a build-up of grit in your pool, as the filter will no longer work properly.
If you switch the flow mode from filtration to backwash while the pumps are still operational, it creates a change in directional pressure up to 100 pounds per square inch. Over time, this force will crack laterals, opening them wide enough to emit sand into the water-return line, where it flows into the pool with filtered water. Older laterals also may fail after regular use, and emit sand from the filter into the pool.
Because water is constantly rushing over the sand in your filter, it erodes at rates much faster than normal, particularly if you operate a high-pressure or high-rate sand filter. Sand coming into the pool from the filter may have simply eroded to be small enough to fit in through the laterals' openings. You will need to remove all the sand from your filter, to check for cracked laterals anyway, so plan on refreshing your filter with new sand, as a maintenance effort, if you replace or check your laterals. - Above-ground pools are frequently laid on top of a sand bed, which easily provides a smooth and level surface on which to lay the inner membrane or pool liner. This sand bed is designed to eliminate punctures in the membrane, caused by stones and other sharp objects surfacing in the soil. However, if it becomes punctured, sand may seep through the holes and settle on the pool floor.
- Do not rule out environmental sources, as the reason you have sand in your pool. Nearby streets, playgrounds and fields are full of fine grit that may become airborne, with wind or passing cars. If your pool is in a high-traffic area, the grit may be blowing in from outside the pool area, suggests Pool Wizard. Also, if you live in an area with slightly sandy soil, you can carry the sand into the pool, via your feet.
