Sand Filter allowing DE to pass through (I think)

JABRY5

Active member
Apr 25, 2020
26
Coppell, TX
I have recently completed a SLAM and added DE to my sand filter to catch the finer particles still in the pool, to get that crystal clear water.

I followed the instructions from this site to add enough DE to raise the pressure by 1 psi. I saw the pressure rise even more over the next 30 minutes once it started catching the finer particles. But then something strange happened - the pressure over the next several hours reduced to its base pressure. What's more - I saw what looked like a fine white cloudiness coming out of the jets. The combination of these two events leads me to believe that my sand filter didn't "catch" the DE, and allowed it to pass back through to my pool.

Does this mean my filter needs another deep clean? I cleaned it for 4 hours about a month ago.
 

pymalion

Member
Aug 9, 2015
7
Atlanta, GA
I have recently completed a SLAM and added DE to my sand filter to catch the finer particles still in the pool, to get that crystal clear water.

I followed the instructions from this site to add enough DE to raise the pressure by 1 psi. I saw the pressure rise even more over the next 30 minutes once it started catching the finer particles. But then something strange happened - the pressure over the next several hours reduced to its base pressure. What's more - I saw what looked like a fine white cloudiness coming out of the jets. The combination of these two events leads me to believe that my sand filter didn't "catch" the DE, and allowed it to pass back through to my pool.

Does this mean my filter needs another deep clean? I cleaned it for 4 hours about a month ago.
I came to the forum today to post this exact same question, basically - weird. Like you, I have often experienced this pressure increase and then drop after adding DE to my sand filter. For example, just yesterday I put some DE in and kept an eye on the pressure. It continued to rise until the pump shut off over night. This morning when I checked the pressure again it had dropped down notably. Not all the way down to the clean filter pressure, but several psi lower than what it had been when it shut off last night. I've never personally noticed what appeared to be cloudy water returning to the pool, but I suppose it is still a possibility that at least some of the DE somehow worked its way through the sand and to the pool.

Maybe someone else will have a better explanation.
 

JABRY5

Active member
Apr 25, 2020
26
Coppell, TX
Good question. It was pool DE. I suppose the cloudiness could have been dead algae caught in the filter too - but it looked like DE to me, and either way it seems I have the same problem. Stuff forcing its way through the filter. Has anyone had any luck with sand filter cleaners?

For what it's worth in diagnosing this, I had a bad problem with both algae and scaling last year before I came to TFP. Does calcium gum up the sand?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,634
San Dimas, CA (LA County)
Good question. It was pool DE. I suppose the cloudiness could have been dead algae caught in the filter too - but it looked like DE to me, and either way it seems I have the same problem. Stuff forcing its way through the filter. Has anyone had any luck with sand filter cleaners?

For what it's worth in diagnosing this, I had a bad problem with both algae and scaling last year before I came to TFP. Does calcium gum up the sand?
I doubt the sand calcified, but it could be glued into a solid mass with suntan oil or other gunk. And then at some point, it breaks apart into chunks. And whatever comes into the filter slides right through the crevasse because it is less resistance than gong through the sand. The next step is a deep cleaning and inspection. If you or your pool guy ever used clarifier or flocculant, you might be looking at replacing the sand.
 

JABRY5

Active member
Apr 25, 2020
26
Coppell, TX
Thanks Richard. Is there a surefire sign that clarifier or flocculant has ruined my sand? Will even the deepest of cleans work to restore it? Both clarifiers and flocculants were used last year.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
23,634
San Dimas, CA (LA County)
Thanks Richard. Is there a surefire sign that clarifier or flocculant has ruined my sand? Will even the deepest of cleans work to restore it? Both clarifiers and flocculants were used last year.
You'll know if you start poking around and the clods won't break up. Deep Cleaning a Sand Filter

Although if I had a place to dump the old sand, I think I'd just replace it and be sure.
 

JABRY5

Active member
Apr 25, 2020
26
Coppell, TX
So...your comment, Flying Tivo, pointed me in a direction I had not thought to look. Reading up on this a bit more...I have a Centurion B855 2-horse single speed motor that runs at 3450 RPMs. Any ideas how to convert that to GPM so I can determine if I'm damaging my equipment?