DE back flowing into pool

[DHinNC]

Recently I replaced the DE filter grids without any issues. Just observed that the filter is back flowing through the pump when the timer shuts off. I don't have a check valve between the pump and the filter. Could this be a problem with the multiport valve on the Pentair DE filter? The DE doesn't get back to the pool when the pump is running, only when the pump shuts off.

Any suggestions?

 

[Ajayabb]

Sounds like a bad seal on the multiport valve to me

 

[Charlie_R]

Is it coming out the return or coming back through the pump? If pump, make sure you released all the air from your filter.

 

[DHinNC]

Yes it's coming back through the filter. There is no air in the filter. It is siphoning back into the pool through the skimmers and main drain. Never had this happen before.

 

[DHinNC]

Is a bad seal in the multiport valve the most logical cause of this issue? There is a lot of cavitation like noise coming from the valve.

 

[Charlie_R]

Is there air in your pump's strainer basket?

 

[DHinNC]

No air in the basket, but not too long after the pump stops I can see through the clear cover that the DE flows back into the filter basket.