Brand new Pentair FNS Plus DE Filter with high pressure?


LifeTime Supporter
I just had a brand new DE Filter installed not more than an hour ago. After the pool guy left, I went and checked things out and noticed that the pressure gauge was at 18 or 19 psi. The writing on the guage shows that the starting pressure should be about 11psi and once the filter reaches 20psi it should be cleaned.

Is it just me or does my reading of 19 sound a bit too high?

I have a call in to the installer, but I wanted a second opinion.


Well-known member
Apr 22, 2008
Central Texas
He may have put too much DE into it. I have their 60 SF model and it reads 13 psi (with a really sad looking gauge) after a backwash and new DE. Mine is the older Nautilus model, but I doubt that they changed much inside. I have 8 grids inside of mine.

(BTW, we might have been neighbors at one time, I used to live in the Vicksburg subdivision just off of Hwy 6 in Missouri City). ;)


LifeTime Supporter
I was thinking about doing a backwash to see if it cleared things up. I guess it can't hurt.

As to being neighbors, we probably were. We finally moved from Quail Valley after 33 years to Sugar Land. We probably ran into each other at the grocery store and didn't even know it!


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
When a DE filter is first installed it gets lots of things out of the water that were getting through the old filter or came with the fill water. You may need to bump or backwash the filter several times before it cleans up the water and settles down to more normal operation.


LifeTime Supporter
May 21, 2007
Cape Coral, FL
DE Pressure

My pool when new read 20psi on my DE filter outlet (press gauge on the top of the DE tank)when the pump was first started without DE loaded. After loading 6lbs of DE, pressure raised 1psi. This is my third year on my Pentair DE 60ft3 DE filter and it works great, and DE pressures have not changed.

I have read here that your filter DE press is totally dependent on the system head losses. Some pools will have lower head losses and thus lower operating pressure