Pressure change after turning pump off and back on.

[tmorrison22]

I have a reoccurring situation that I can't find an answer to.

When I am using DE in my filter, which i do occasionally, I normally let the pump run until the pressure rises to a point where I feel I need to backwash. This usually happens in about 10 hours or so. My nominal pressure is 12 psi and backwash at about 18 psi, when using DE.

The head scratcher for me is if at the 18 psi point I turn the pump off for a few minutes and back on the pressure will return to 12 psi. I have tried this a few times and the same thing happens. I just cant figure out why the pressure wouldn't return to the same pressure it was before I turned off the pump.

Any ideas? Thanks in advance.

 

[mknauss]

The DE is getting fluffed up by a bit of back flow. Does the pressure rise back realtively quickly?

You should backwash when your filter pressure rises by 25% over your clean filter pressure. At 12 psi clean, that would be 15 psi.

 

[tmorrison22]

I have let it run a few hours after the power cycle and the pressure remained at 12 psi. Like I never added the DE in the first place.

 

[RedBluePool]

Pressure gauge could be bad or bent. If the dial is bent foward the need gets stuck.