Pump Pressure Rising on DE filter grid inground pool, please help!

[PapaAlan53]

I'm hoping some experts out there can figure this out.
So I have an in ground pool 17k gals or so, pump runs approx  3200 rpm, DE filter tank with grids.  Past several years, the pressure has stayed around 10psi but lately with new DE filter grids, the pressure is fine for a few hours but then rises over 20psi.
Backwashing brings it back to 10psi for perhaps 30mins and slowly starts to climb again.
I slowed down the variable pump to 2500 and roughly the same happens.
If I remove the DE filters completely just letting water run through the tank, the pressure stays at 10psi no climbing at all for days.
I thought, hmm is it the quality of the filter grids, is it the manifold replacement for the grids, what could cause the pressure to rise when grids are in and completely clean and yet pressure be fine without grids installed?
 

I really need help on this!

[waterbear]

Are the grids OEM or third-party? Are you overcharging with DE? Have you cleaned the grids before using them? Is the manifold clogged? Is the new grid seated properly? Did you break down and clean the filter when you replaced the grids? Many things can be happening and these questions can help us narrow things down 

Let's start with the make and model of your filter and your pump. That would be a very useful starting point and we can take it from there.

[PapaAlan53]

Brand new third-party grids, had this problem even on original oem grids.  Nope DE correct according to charts and local pool company, 17k gal.  Hosed down new grids and cleaned.  Manifold appears completely clear.  Grid seated correctly.  Yes broke whole assy down, cleaned etc. upon grid replacement.  filter is DE6000 hayward, pump is new but old pump used i had same problem.  Just setting variable speed on current pump to 2500 rpm still see rise after hours.  Experimenting tomorrow.

[waterbear]

How did you clean the grids?

 

[PapaAlan53]

drained the filter tank and removing the clamp around the tank or undoing the bolts, Remove the manifold and each grid, then use a garden hose to flush out all the DE from the filter grids. then removed grid assy and garden hose the outside of grids completely.

Edited March 16 by PapaAlan53
mistyped

[waterbear]

Did you use any chemical cleaner or acid wash? This is a new grid, correct? One that has never been acid wadhed?

[PapaAlan53]

yep, brand new grid, no cleaner or acid wash.  At this point with multiple tank drains and refills and cleaning grids with new DE every time, it appears for some reason to be holding 10-15 psi ok.  Will do one more backwash, drain and clean and see how it goes.

[waterbear]

Glad it's resolving itself. Might have been air trapped in the grid or some residue from manufacturing stuck that has worked its way out. The other possibility is the filter was doing it's job and removing something from the water and after repeated cleanings whatever was there gas been filtered out. The fact that g at you said that when you remove the grids and just let the water flow through the pressure stays at 10 PSI but once it's actually filtering the pressure rises. Also  consider that since the plumbing and tank have 10 PSI of backpressure that itcWILL be higher once the fully  charged grids are installed. You want to check the pressure on a newly cleaned (not just backwashed) setup and backwash when the pressure rises 10 PSI above baseline. If time between backwards become short it means it's time to break it down and clean it.

[PapaAlan53]

Thanks, I appreciate all the time you spent thinking about this weird situation!