Small particles not being filtered by sand filter

amy6152

Member
Apr 4, 2017
11
Rochester, NY
When we opened the pool this year, we had a lot of algae. SLAMed it, then had a bunch of dead algae at the bottom. When I'd vacuum it up, you'd see a cloud coming out of the returns. Figured something was broken inside my sand filter, so I had the service tech come out. He took everything apart, said there were no problems, and put it back together. I've been out of town since then, and my husband had a hard time getting the water clear. I'm home now and working on it. Got the chemicals in line (ph was way off), but it's still not clear this morning so I threw some DE into the skimmer basket and got HUGE plumes from the returns. Something is wrong, right?? Because the pool tech who was out here told me dead algae is too small to be caught by the sand filter and I needed to vacuum to waste. But I'm now wondering if he was full of boloney and I paid him for nothing when there really was a problem. Add to that, I wasn't comfortable taking the filter apart myself, which is why I called a tech to begin with. Was that a mistake?
 

amy6152

Member
Apr 4, 2017
11
Rochester, NY
I'll add, he also saw the bottles of bleach on my porch and told me that's why my pool was cloudy. Because I was using the wrong kind of bleach!! I needed the one from the pool store!! You can see why it wouldn't surprise me if he was wrong about the filter.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
10,878
Evans, Georgia
Uh, yeah..... he knows bupkis about liquid chlorine....

Vacuuming to waste certainly helps get the dead stuff out of the system, but the DE also should have helped trap small stuff too which you could then backwash out. Actually the sand will work but its the slowest on its own.

Since he supposedly took the filter apart, he would have fixed any channels in the sand when refilling. Could he have missed a broken lateral?? Hmmmmmm.....that might be one reason you see schmutz returned to the pool.

I'll admit I've never done it myself but am preparing to do so soon...so I understand from reading its not too hard...but I think YOU need to get into the filter and inspect it. I'll look for the directions and post them for you.

Maddie :flower:
 

sande005

Member
Aug 19, 2018
9
White Bear Lake, MN
I'm no "pro", and my system is almost 20 years older than yours, but I'll hazard some possibilities:
1. The obvious - the selector (multiport) on the filter is set to a recirculate position, rather than filter.
2. The filter needs a good backwash, and rinse. Mine will plume somewhat, when I have overloaded it with algae. Also see the thread about deep cleaning sand filters.
3. The "spider gasket" inside the multiport is torn, allowing water that should be going to the filter instead to go directly to the returns.
4. The filter is low to very low on the proper amount of sand.
5. You are right, and one of the pipes inside the filter is broken (but that is very unlikely, unless you had freezing damage over the winter).

Mine does not do a great job of handling algae - in cases where it has really gotten away from me, I'll kill it by shocking. Then vac to waste. In bad instances (or if the vacuuming has stirred it up and clouded the water), I may then have to use floc to drop the suspended to the bottom, and then vac to waste again. I may have to repeat. Can take a week (or even two!) to get everything right. Mild amounts seem to filter out, but if it gets heavy, time to vac to waste.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
10,878
Evans, Georgia
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
22,059
San Dimas, CA (LA County)
When we opened the pool this year, we had a lot of algae. SLAMed it, then had a bunch of dead algae at the bottom. When I'd vacuum it up, you'd see a cloud coming out of the returns. Figured something was broken inside my sand filter, so I had the service tech come out. He took everything apart, said there were no problems, and put it back together. I've been out of town since then, and my husband had a hard time getting the water clear. I'm home now and working on it. Got the chemicals in line (ph was way off), but it's still not clear this morning so I threw some DE into the skimmer basket and got HUGE plumes from the returns. Something is wrong, right?? Because the pool tech who was out here told me dead algae is too small to be caught by the sand filter and I needed to vacuum to waste. But I'm now wondering if he was full of boloney and I paid him for nothing when there really was a problem. Add to that, I wasn't comfortable taking the filter apart myself, which is why I called a tech to begin with. Was that a mistake?
Did you see him? Did he really take everything apart? That would involve a tarp and heaps of wet sand or more likely, a bill for new sand. You'd likely see a mess or a bill.

A sand filter is capable of catching anything large enough to see with the naked eye -- and that includes DE particles. There are channels in the sand or cracked in the plastic innards or a crack in the multiport. Something is letting debris cross the dirty/clean barrier, which is the top of the sand.