DE Filter Post-SLAM - Pressure back DOWN???

Petebacher

0
Bronze Supporter
Jun 19, 2017
22
Kennett Square, PA
Greetings All -

First post - been lurking since last August when we bought our new home with a 30k gal in-ground pool.

All had been good so far this year until late last week when I let chlorine drop to .5. CYA is approx 55. Water immediately went cloudy and filter pressure jumped up 4 psi to 25 psi!

Filter is a large Waterways DE filter (I forget the size - it charges with approx 7 lbs of DE) which I cleaned thoroughly and recharged at the beginning of the season.

I have been chlorinating using liquid "Shock" (no CYA) which I then used to bring the pool up to ~28 for a run of SLAM. Filter psi continued to climb, peaking around 7 psi over what it had been running at for the past several weeks.

The water's been clear since Monday, and last night I completed the SLAM (1 ppm FC drop overnight) so I'm now allowing the FC to drop back to around 9 per the FC/CYA table.

The thing I don't understand is that my filter pressure has DROPPED BACK TO 21 psi, where it started prior to these problems!! Do DE filters have the ability to "self-clear" after recently being cleaned and charged? This sounds strange to me...

-Pete
 
Mine did the same thing after a SLAM only on a smaller scale. I was at 9 (clean) then it went to 11 and then back down to 9 after the SLAM. We will be taking ours apart for a thorough cleaning this weekend but I thought it was odd too and wondered if it happened to others.

ETA: we never shut off the pump during the SLAM or after.
 
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