The Filter

If the pump is the heart of a swimming pool or spa, then the filter is its lungs. The filter removes impurities and particulate matter (oils, grease, and dirt) and returns clear water to the pool via the return lines.

If the skimmer and pump do their respective jobs efficiently, the filter does a better job. It is the filter-in combination with chemicals -- that makes the water sparkle and safe to swim in.

Three types of filters are used primarily for home swimming pools:

• The high-rate sand filter
• The cartridge filter
• The diatomaceous earth (D.E.) filter

What these three types of filters have in common is that they all need to be regularly cleaned. A dirty filter simply can't do its job effectively. Consequently, the pool water becomes cloudy, the pool walls become laden with algae, and chemicals can't be evenly dispersed into the water. Moreover, a dirty filter causes a build up of pressure in the system. This heightened "back pressure" diminishes flow and puts undue stress on the pump motor.

The best time to clean a filter is before the water becomes cloudy. To determine when a filter should be cleaned, monitor the pressure gauge that sits atop the filter tank. While filter pressure varies with different filter styles and systems, pressure usually ranges from 6 to 20 pounds per square inch (psi). It's time to clean the filter when the pressure has increased by 8 to 10 psi above normal.