Sand in a Pool Caused by the Filter

Multi-Port Valve

Modern sand filters come with a multi-port valve that allows a multidirectional flow of water through your sand filter. These ports can include several settings that include one for filter, rinse, backwash, recirculate, drain and closed. When you backwash a filter, you must switch the multi-port valve to the rinse setting. It can be that the valve is slightly opened and didn't lock in place when switched back to the filter setting. Turn the filter off and turn the valve from rinse to filter again to ensure it's locked in place on the filter setting.

The internal composition of a sand filter involves the use of several laterals. These are tubes that extend from a PVC core with screens covering the outside of the laterals. These laterals allow water to pass through them, but not the sand and trapped dirt. The water moves through laterals and back out the filter. When a lateral is cracked, sand will enter your pool water. This is one of the more common reasons for sand in your pool water.

A special grain of silica sand is used for sand filters. This sand is coarse enough to trap dirt and debris as small as 25 microns in size, and porous enough to allow water to freely pass through as well. The silica sand used is 45 mm to 55 mm in grain size. If the sand is passing through the laterals, even if they are not cracked, it could be a result of the sand grain. If the sand is too fine, it will pass through the lateral and into your pool.

The sand inside a pool filter is meant to stay inside for a long time. The average time frame for sand replacement inside a filter is about five to seven years. Many pool owners, however, have experienced longer periods without needing to change the sand. The sand may need to be replaced if you find yourself needing to backwash the filter more than usual. The average backwash period for a normally operating sand filter is about once per month. Over time, calcium deposits attach themselves onto the sand. This forces the sand to lose its coarseness and effectiveness, prompting the more frequent need to backwash and clean the filter.