Sand Filters - are they really this bad?

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My info is (as stated in my signature): 16x32x8 vinyl in-ground; 20k gal; Pentair SuperFlo 1HP; Hayward S-200 sand filter; 1.5" plumbing; solar heating; 1 main drain, 1 skimmer, 1 return with 2 jets. I backwash when the pressure reaches about 22 lbs (after BW, it's around 14). Although, the last few times I've tried vacuuming and saw the silt come back out of the jets, the pressure didn't rise. That makes sense if the filter isn't catching anything.

I'd thought of vacuuming to waste, but I don't think that's the answer. The fact that I saw the DE go straight from the skimmer and out the jets indicated that there was something else going on.

I removed the sand to check out the laterals and internal plumbing. The laterals looked fine - until I tried to unscrew one and snapped it in half. Doh. I went ahead and ordered a new set of laterals and gaskets. All the laterals and gaskets are super brittle and I figured it wouldn't hurt to replace them.

While I had the filter disconnected from the multiport, I switched the valve to recirculate and turned on the pump to see if there was any leakage. Not a drop came out of the filter pipes, so I think the multiport is in good shape.

I'm starting to think I had some sort of channeling issue. I wish I'd found the forum that mentioned overflowing the filter with a garden hose to clear any clumping and gunk before I removed the sand to see if that would help. Oh well...

Also, pH is 7.2 and I did dump in about 20lbs of bicarb a couple of weeks ago. What's a good vac/bw schedule? Maybe I need to go get pool schooled for a little while.
 
Fwiw I have seen Bicarb added to a pool and result in a fine powder silt on the pool bottom and had that powder pass through a cartridge filter when vac'ing :scratch: . The only fix for the problem was to vac the pool to waste using a portable pump and discharge hose to the driveway. There was no history of this happening before, and in the years after it was never a problem again.

As for your backwash schedule I think that there are other factors that should be considered beyond rise in filter pressure. I know that your owner manual probably says 6 to 8 psi rise then backwash, and one might claim that the filter even removes a finer particulate with a layer of dirt on top of the filter sand, but going beyond 3 weeks between backwashing is just asking for trouble in the long run. IMHO. That is a big pool with an undersized filter that is paired with a pump that is probably toward the wrong end (too large) of the too small too large scale (someone help me with flowrates), and if it were my setup I would be backwashing weekly as to avoid the long term problem of sediment working its way down through the sand. This may be one of those combination of multiple things happening and/or culminating at this time and resulting in the troubles you are having. But know for the future that with broken laterals, there will be no doubt with the sand dropping into your pool below the return.
 
Pooldr gave you the conventional backwash thinking, however, it is incorrect. I personally backwash my filter once or twice a year. There are lots of others that do the same thing. None of us have any sort of problems.

First thing I'll say is that your filter is kind of small for your pool, but that just means that you may have to backwash it more often.
If it's bypassing dirt back to the pool there's either something wrong in the filter or in the multiport valve. Since you took care of the sand/lateral part, if it's still returning dirt to the pool I suspect the multiport. Did you take it apart?
 
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