The first sign that you should have your swimming pool filter cleaned is high pressure. All filters have a pressure gauge on the top of the filter. Normal swimming pool filter pressure should stay between 15 and 25 psi or pressure per square inch. Check the pressure gauge to see if your filter pressure is high, low, or normal. The calendar will also tell you if it is time for a swimming pool filter clean. All of the major pool manufacturers (Jandy, Hayward, and Pentair) recommend that a pool filter should get cleaned at least once per every six months. Many swimming pool professionals suggest that a pool filter should be cleaned even more often. If you have had a filter clean over six months ago, even if the filter pressure is in normal range (15 to 25 psi), it is time for a filter clean. Also if you have high foliage in your back yard like trees, bushes, flowers, then your filter may need to be cleaned more often than a pool with no to little foliage around it. Also check the circulation in the swimming pool.
If a customer calls our office letting us know that circulation is weak or nonexistent in the swimming pool, we always check for high filter pressure. Are the wall fountains and shear descent fountains at their normal height? Is the water feature in the middle of the spa as tall as it usually is? Is the flow of water coming out of the return jets in the swimming pool weak or strong?