Sand Filter Gurgeling

Why does it sound like my sand filter is always trying to fill with water? But yet the return flow into the pool is good.


Hi. It sounds like air getting into the system. Air bubbles in a sand filter will make a gurgling sound.

Air in the system can be caused by not enough water in the skimmer, or something blocking the skimmer causing it to empty faster than it can refill. If the skimmer seems OK I would check the hair and lint pot.

The hair and lint pot is the most common cause of suction side leaks. Most pots anymore have a clear lid so you can see into them. You should not be able to see any air at all. If this is the problem you could try putting aqua lube on the o-ring and see if that seals it. The o-ring could be replaced as the next step. If the lid has a lot of sideways play in it the housing may be warped and need replaced.

Another cause of leaks might be the hose connections on the hose going from skimmer to pump. Most suction side air leaks will drip water when the filter is turned off. That is a pretty easy way of finding the leak.

Air bubbles in the return flow are a good indication of a suction side air leak. The filter will still function normally, with a strong flow in most cases, but you should be able to see air bubbles. If there are no bubbles in the return and no air leaks then there might be a problem in the valve assembly. Rotary valve assemblies use a spider gasket that needs replace occasionally. Water dripping out of the backwash port when the system is in the filter position is a good indicator of a worn spider gasket.