My pool pump and I are in an epic battle. So far, I am losing. About a month ago, it started losing pressure and making a loud gravel sound. My friend says it is cavitating. Water flow into the pool decreases significantly when it does this. Well, that set in motion a series of events to fix the problem, but to no avail. We cleaned the filter. A service person inspected the impeller, which was fine. But the neck to the diffuser was completely broken off, so he replaced it. We also replaced and lubed o-rings. A mechanic friend took the motor apart and inspected it; it was fine. He also connected it to his pool and it worked great without any problems. We used a drain king to flush the skimmer and main drain lines, the service person tried to blow them out with high powered air. I also rented a 50-foot drain auger and used it on the main drain line. I really thought it was a clog in the main drain, but now I'm having my doubts. We also used shaving cream and inspected all of the suction side pvc for possible leaks and found none.
Here's the problem: I will prime the pump and start it, and it sounds good and works well. Runs about 20 psi. Then after 20 minutes or an hour or 4 hours, it suddenly drops pressure to about 10 psi and the motor sounds rougher and louder. Water flow into the pool and spa goes down. As time goes by, the pressure continues to drop. However, the pump doesn't seem to lose prime when it drops pressure. No air bubbles in the strainer basket to speak of. I will switch the suction value from skimmer to MD and it doesn't make any difference whatsoever. One potential issue is that it appears the hose to the automatic cleaner in the pool may have leak(s) at some of the connection points. Btw, the pressure seems to go down quicker and more severe when the cleaner is running. However, even if the cleaner is not on, the pressure on the pump still eventually drops from 20psi to 10psi and sounds rough.
Any thoughts, ideas, suggestions are greatly appreciated. Now my water is dark green and if you threw in a few lily pads, it would look more like a coy pond than a pool. Thanks!