Hydrostatic Main Drain Valve


Mar 7, 2016
Arlington tx
Here's a question for you scholars. Pool Water has been dropping at a fast rate. Did the bucket test, and the pool lost 1/2 inch of water from the bucket and over 11/2 inches from the pool in 24 hours. I've dye checked everything but the main drain and can see no signs of a leak. There are no leaks with anything on the equipment pad. I've done a lot of reading and have my suspicions its in the main drain area. I haven't dived down yet to remove the cover and check things out since the water is only 72 degrees. My question is, can a bad hydrostatic valve leak water out but yet let air in. The reason I ask is that when I turn my jandy valve on to just main drain suction I get a lot of air in my pump basket, but when on just skimmer suction the pump basket is clear. Anyone have any ideas??


LifeTime Supporter
Aug 19, 2014
Pacific NW
I had some clogging in my main drain (pine cones) that caused the same symptom when
I filtered or drained with main drain only. So possibly?


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
Aug 10, 2012
FL panhandle
Sounds like a suction leak on the main drain line that sucks air when the pump is on and leaks water when the pump is off. I doubt you have a hydrostatic valve, I've never seen one installed in DFW.