I have a C751 Hayward Cartridge Filter, I keep hearing a rumbling noise in filter when power isturn off. It sounds like it is loosing air in the tank.
Have replaced the 0-Ring on locking knob, and 2 fibre washers and also replaced directional vent valvw w/o-ring.
Can you help with this problem.

Question

I have a C751 Hayward Cartridge Filter, I keep hearing a rumbling noise in filter when power isturn off. It sounds like it is loosing air in the tank.
Have replaced the  0-Ring on locking knob, and 2 fibre washers and also replaced directional vent valvw w/o-ring.
Can you help with this problem.

Hector F. · Accepted Answer

For something like this there are multiple possible reasons. What is occurring is air is being released from the system causing loss of pressure hence water flowing back into the pool. This could be caused by bad o rings, seals, or valves. A tech on site is your best option to go through the process of elimination.

Question Regarding: Star Clear Plus 75 Sq Ft. Filter 1 1/2" Ports

I have a C751 Hayward Cartridge Filter, I keep hearing a rumbling noise in filter when power isturn off. It sounds like it is loosing air in the tank. Have replaced the 0-Ring on locking knob, and 2 fibre washers and also replaced directional vent valvw w/o-ring. Can you help with this problem.