Out put sending dirty water back to pool when vacuuming to waste

[FlamingoSister]

i have a hayward sand filter with a multi port valve. We replaced the valve and the sand this spring And replaced all o-rings. I used floc last night and when Inwent to vacuum to waste this morning the jet was returning dirty water to the pool. we are at a loss. The pump is strong and working properly. No leaks when it is in filter or recirculate. Any suggestions? We took the valve off again this morning and checked everyting. It all looks good.

 

[Texas Splash]

When you place the MPV to WASTE, no water should be going back to the pool. Doing so would indicate that floc may have entered the filter and ruined the sand as well. A big reason we avoid floc 99% of the time. Perhaps the MPV label is not on correctly or the valve was installed incorrectly? Not sure, but when that handle goes to WASTE, it should bypass the filter completely.