I have a Pentair Challenger Pump and salt water pool with fountain water feature (no spa). The water feature will slow down for 30 seconds and then be normal for 30 seconds, on and on while the pump is on. While looking at the pump, the water is whirling around great for the 30 seconds the pump keeps its prime and then for 30 seconds the water goes down and makes a humming sound but isn't swirling around like it should. I replaced the O ring with lubricant, just in case it wasn't holding the suction but that didn't fix it. I don't think it was the O ring to begin with but I figured it was a cheap and easy way to eliminate that issue.
Any suggestions? Thanks in advance.