New Sand, Now Weak Return Flow

PopcornGirl2

Bronze Supporter
Mar 24, 2011
49
Baton Rouge, Louisiana
#1
Hi Everyone,

It's opening season here in south Louisiana and I thought I was doing everything right. I got my levels stabilized and I used SLAM method to get my water crystal clear. However, we noticed that our filter wasn't working as well as it has in the past, and the suction seemed to be consistently decreased. A friend recommended that we change out the sand in our filter since it is almost eight years old. Pool guy came out on Monday and changed out the sand for us, and added small amount of DE to help with new sand filtration. But ever since the change, my filter pressure has been super high (25-30) and my return flow is very weak. Needless to say, our automatic pool vacuum is not working well, either, so now there is debris (leaves, grass) on the bottom of my pool. The water is still clear, but it won't stay that way long if I don't get this cleared up.

When I backwash the filter, the pressure drops to 10-15 and the outflow from the jets is strong, but after fifteen minutes or so, the pressure goes back up and the return flow becomes weak again. Both the skimmer and the pump basket are clear of debris and there isn't anything caught in the vacuum.
Any idea what could be causing this??

I have a Pentair Sand Dollar Sand Filter that is between seven and eight years old.
Thanks in advance for any advice you can offer me! :)
 

Flying Tivo

Well-known member
Jan 24, 2017
532
Monterrey, NL, Mexico
#2
Maybe too much DE was added, but you backwashed and most of the DE should be gone by now. Could the pool guy have misassembled the multi-port or laterals?? Maybe too much sand or the wrong type of sand? Im assuming the system was working perfectly before. FYI sand dose not get old you just have to clean it.

Felipe
 

PopcornGirl2

Bronze Supporter
Mar 24, 2011
49
Baton Rouge, Louisiana
#3
Thank you Felipe! Well, Jose has been our pool equipment guy for years and really knows his stuff, so I find it hard to believe it's that... In fact, he installed this filter when we first bought it. I guess anything is possible though. I'm just wondering if it could be anything else before I have him come all the way back out here.
 

proavia

LifeTime Supporter
TFP Guide
Feb 6, 2015
1,100
Chandler AZ
#4
Sounds like a possible chemistry issue. If the filter pressure rises that quickly you may still have an algae problem.

Can you post a full set of test results, including water temp. Also, you may wish to do an OCLT to rule out any nascent algae issue.
 

PopcornGirl2

Bronze Supporter
Mar 24, 2011
49
Baton Rouge, Louisiana
#5
Sounds like a possible chemistry issue. If the filter pressure rises that quickly you may still have an algae problem.

Can you post a full set of test results, including water temp. Also, you may wish to do an OCLT to rule out any nascent algae issue.
Okay, well, I kept chlorine at SLAM levels for over a week, but here are my latest test results:
FAS-DPD FC -- 4.5
Total Chlorine -- 5.0
CC -- 0.5
PH -- 7.6
TA -- 100
CYA -- 30
Calcium Hardness -- 280
Temperature -- 72 degrees
Water is crystal clear. No signs of algae, green or black. No cloudiness.
 

PopcornGirl2

Bronze Supporter
Mar 24, 2011
49
Baton Rouge, Louisiana
#7
Well, it turns out that my pool guy was right... apparently, it's normal to have to backwash a lot right after changing the sand in a pool filter. Old sand, new sand, DE, etc. can get stuck in the line. After about 10 backwashes over the past week, the problem is completely resolved and my outflow is stronger than ever! Also, my filter pressure has settled down to a normal 10-15. Thanks for all the input. This was quite a learning experience for me. ;)