Pressure shooting up after new sand and laterals

PointeTaken

Bronze Supporter
Aug 28, 2019
143
Hoover, AL
Pool Size
12000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
Had a small fissure in the standpipe of my lateral assembly, so I had to swap out the assembly. While I had all the sand out, I decided to go ahead and put new sand in there. It’s never been changed since I’ve owned the pool and who knows if it was ever changed by the previous owner. I know the prevailing theory around here is that sand doesn’t really need to be changed out, but I did it for the heck of it. Anyhow, once I got everything replaced and put back together, I ran a backwash, and then ran the pump at high speed to purge air. I noted my new baseline PSI at 8.5, which is 0.5 PSI below my old baseline. I checked the pool and the plumbing periodically for a couple hours after that and everything was fine. PSI had increased to 9, no leaks, everything seemed normal. Finally, about 5 hours after starting everything back up, I was getting the grill started for dinner and noticed that the water in the pool seemed too still. I went down to the equipment pad and saw that my filter pressure was at 15; my returns were putting out much less pressure than usual...about as much as they do when I have the pump speed turned way down. I backwashed, and my PSI returned to normal. I just went back out again after cleaning the kitchen and the gauge is reading just under 14 (about 2-3 hours later). What gives? Is the new sand just catching a whole bunch of fine particulate that the old sand wasn’t? I’ll add that the Tiger Shark was doing it’s thing for a couple of hours late this afternoon. Could some of the fine sediment in the pool gotten stirred up and finally captured by the filter?
 

mknauss

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May 3, 2014
44,029
Laughlin, NV
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Pentair Intellichlor IC-40
What sand did you use?
 

mknauss

Mod Squad
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May 3, 2014
44,029
Laughlin, NV
Pool Size
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OK -- good. We know of issues using Quikrete sand.

Let's see if some of our sand filter experts will chime in ---
 

PointeTaken

Bronze Supporter
Aug 28, 2019
143
Hoover, AL
Pool Size
12000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
We know of issues using Quikrete sand.
Yeah I’ve heard horror stories. I peeked in an open bag when I was at Home Depot one time and thought “gee...no wonder.”
 

PointeTaken

Bronze Supporter
Aug 28, 2019
143
Hoover, AL
Pool Size
12000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
Note: I backwashed again this morning; filter pressure only settled at 9.5 PSI afterward. I did notice a small amount of very fine sand settled in the sight glass on the multiport. I figured that’s just residual and most would have been washed out with the backwash. A handful of the new sand is about the same coarseness as the old sand. We’ll see what happens in the coming hours.
 

PointeTaken

Bronze Supporter
Aug 28, 2019
143
Hoover, AL
Pool Size
12000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
is this the procedure you followed?
Yes, to a T, and I used 250 lbs. That said, the final sand level was nowhere near 6 inches from the top of the tank. When I was leveling the sand out, I'd say the opening of the tank was at about the thickest part of my forearm. So maybe 9 - 10 inches?
 

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
2,505
Chandler AZ
Pool Size
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Plaster
Chlorine
Liquid Chlorine
Filter pressure rising pretty rapidly is usually an indication of a chemical issue, not a filtering issue. Although there may be something going on with your filter since you just change the sand. That being said, post a full set of test results and also do an Overnight Chlorine Loss Test to help rule out a nascent algae bloom.

FC
CC
pH
TA
CH
CYA
Water temp
 

PointeTaken

Bronze Supporter
Aug 28, 2019
143
Hoover, AL
Pool Size
12000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
Yes, I went ahead and ruled that out as a matter of course. OCLT was zero.

I thought I had it set so you could see my PM log, but here goes:

FC 5
CC 0
pH 7.6
TA 70
CH 120 (Adding later this week)
CYA 50 (Lost a bunch a couple of weeks ago when we had 6 inches of rain in a day...I'm adding a couple of pounds once I know I won't have to backwash for a while)
Water temp 79
 

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PointeTaken

Bronze Supporter
Aug 28, 2019
143
Hoover, AL
Pool Size
12000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
Your Poolmath logs are not being shared. Check your settings.
Odd. Sharing is enabled in the PM app. If there's something I need to do on the TFP-end, I can't find the setting.

We’ll see what happens in the coming hours.
After approximately 2.5 hours, my filter pressure has actually decreased to the 8.5 PSI it was at following the initial backwash. I wonder if I didn't get all the fine sand out the first two times. And if that's the case, I wonder if a vac-to-waste of very fine sand is in my future. I'll continue to monitor filter pressure throughout the day.

Edit to add that the gauge is only 2-3 weeks old in case anyone is wondering.
 

PointeTaken

Bronze Supporter
Aug 28, 2019
143
Hoover, AL
Pool Size
12000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Hayward Turbo Cell (T-CELL-5)
Filter pressure is holding at around 8.5 PSI. I'm assuming at this point that the rise in pressure was due to residual sand particulate that didn't get flushed out the first time, combined with my Tiger Shark stirring up a bunch of sediment while it was cleaning. Will update the thread if there is another dramatic increase anytime soon.
 
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