Filter pressure low after sand replacement

[ack1961]

Hello all - been a member for a couple years and have learned a lot from the posts, but I am stumped with this current issue.
I've been battling this one for about 5 days.
After changing sand (5 years since sand replacement), I have an issue where if I'm running on Filter-mode, my starting pressure after backwash is 26 PSI and will quickly (within 2 hours) climb up into mid-30's and I have lost pressure through the system. If I BW and then switch over to Recirculate, the pressure goes to 16 PSI (the usual starting point after BW) and will run like that unabated.
In Filter-mode, there is rattling noise coming from the valve...probably air, but I have tried bleeding with no good results. I've disassembled the valve and see nothing of concern.
I've also swapped out 6-way valves to eliminate the hardware.

System:
I have an 18x40 pool (23k gallons) with a Pentair Whisperflo pump, Pentair 6-way top valve (272526 & 262506), Tagelus TA-60 sand filter, AquaRite T-9 Salt system.

Issue:
I removed the old sand and washed out the tank. Removed and cleaned the standpipe and all of the laterals. No broken laterals.
I added water up to 1/3 of the way and replaced the sand with 325 lbs. of Quikrete Pool Filter Sand. I used a sand diffuser to ensure no sand got into the standpipe.
Went to BW and Rinse and all seemed OK, but when I went to Filter, that's when I heard the noise from the valve and noticed the pressure up at 26 PSI.

Troubleshooting:
I tried bleeding air by opening the bleeder valve before each operation (BW, Rinse, Filter). No change.
I have replaced all of the suction side PVC up to the ball valves (Deep-end, Shallow-end and Drain) including a new union and threaded intake to pump housing. No change.
Replaced/greased the o-ring on Pump Lid. No change.
Replaced all 3 of the unions at the valve and replaced the valve o-ring. No change.
Replaced the pressure gauge and the bleeder valve. No change.
Swapped out the Pentair 272526 (2 years old) with an older 262506. No change.
I removed about 25 lbs of sand. No change.

I've seen posts where folks indicated a suction-side air leak, however, since my system runs perfectly on Recirculate, I would think that suction-side air leak is eliminated as a culprit.
I've also seen mention of Quikrete not being #20 Silica sand and this could be the issue. I know I've used it before (I had an old bag lying around), but I think I used ZeoSand last time.
I think my problem has to be in my sand filter tank, and I am leaning towards just replacing the new sand with ZeoSand and see if that fixes the issue.

I wanted to check with some of the experts here first. Any advice?

Thanks!
Steve

 

[Flying Tivo]

Can you post your Water test Results? What test kit do you have? Please add that to your signature. Dont know much about the quickcrete sand. Iam one of the few with Zeosand, in case you want to go back to it ask me anything. We usually say its a chemistry problem and not a sand problem. I will wait for the test results and advice later. Make sure your filter gauge goes to 0 psi when the pump is off.

 

[ack1961]

Pool water is clear.
Gauge does go to 0 when pump is off. 16 PSI in Recirc, 26 PSI in Filter
Pool water tests fine via Pool-Master 5-way test kit. Ph/Alk are good.
AquaRite Salt system shows 2800 ppm and generating Cl.

Everything was working perfectly before I changed the sand. I changed sand because I could see dirt coming through the jets. I inspected that sand and it was time.

 

[Pool_Medic]

First sand doesn’t need to be replaced every five years.

I assume you disconnected both Lines from multiport to remove the sand, are you certain you now have them reconnected properly?

Snap a quick picture of your pad, it might help us troubleshoot.

 

[ack1961]

First sand doesn’t need to be replaced every five years. It started spewing matter into the pool. Checked the sand, and it was dark green. Mfg recommends every 3-5 years. I've owned this pool for 21 years, so I've done this several times - never been a problem until this go around. The only difference is the media (Quikrete Pool Filter Sand). It was an emergency purchase at HD at 6AM.

I assume you disconnected both Lines from multiport to remove the sand, are you certain you now have them reconnected properly? Yup - ports are properly aligned. Suction side port is slightly higher than Return or BW ports and the PVC lines are rigid, not flexible.

Snap a quick picture of your pad, it might help us troubleshoot. Done.

Thanks for all the replies!

 

[Pool_Medic]

If you’ve done it a lot then I can only assume the issue is with the media you used.

 

[Flying Tivo]

Gauge does go to 0 when pump is off. 16 PSI in Recirc, 26 PSI in Filter
Pool water tests fine via Pool-Master 5-way test kit. Ph/Alk are good.
AquaRite Salt system shows 2800 ppm and generating Cl.

Its not that we dont trust you that the water is "Good". We need numbers so we can help you better.
Fc
Ph
Ta
CH
Alk
Cya
Salt

 

[ajw22]

If you have not passed an Overnight Chlorine Loss Test you can't say your clear water is fine.

And I don't think you can do a Overnight Chlorine Loss Test with your PoolMaster test kit.

 

[ack1961]

Problem solved. Bad sand.
Replaced the Quikrete Pool Filter Sand with #20 silica sand and immediately my system returned to normal. 18PSI on Filter and holding steady.
Water is perfect...

If you’ve done it a lot then I can only assume the issue is with the media you used.

Thanks!