John Faulkner
Member
Every time I backwash and restart, a bunch of sand shoots into the pool through the returns. Happens only for a few seconds but it’s annoying. Any ideas?
Sand blowing back into the pool after backwash
- Thread starter John Faulkner
- Start date
Kevin Marsh
Member
I’ve run into that same issue before and in my case it wasn’t a broken part, it was just the way I was restarting the filter. After a backwash the sand bed inside the filter gets really stirred up, and if you switch the valve straight back to “filter” mode, the loose particles have nowhere to go but back into the pool. That’s why most manufacturers recommend running the “rinse” setting for about 20–30 seconds after every backwash. It settles the sand bed again and flushes the loose fines out through the waste line instead of through your returns.
Another small thing that can make a difference is how fast you start the pump back up. If the system kicks on at full force right away, it can disturb the sand bed more than necessary. I got into the habit of bleeding air from the filter first and then letting the pump prime smoothly, and that cut down the problem a lot. If you’re already doing both those things and still seeing sand, then I’d lean toward one of the mechanical issues the others mentioned like a lateral, gasket, or even sand grade.
Another small thing that can make a difference is how fast you start the pump back up. If the system kicks on at full force right away, it can disturb the sand bed more than necessary. I got into the habit of bleeding air from the filter first and then letting the pump prime smoothly, and that cut down the problem a lot. If you’re already doing both those things and still seeing sand, then I’d lean toward one of the mechanical issues the others mentioned like a lateral, gasket, or even sand grade.
Lily Allen
Member
I had the same issue too, it turned out I wasn't giving enough time for the rinse cycle after backwashing. When I switched the valve back to ‘filter,’ the loose sand had nowhere to go but back into the pool. I now run the rinse cycle for about 20-30 seconds after every backwash and it works great. Anyone else run a rinse cycle after backwashing?
Henry Thompson
Member
When I had sand blowing back, I discovered that my filter was only slightly overfilled from the last sand change. It didn’t seem like a big deal at first, but even that extra couple of inches gave the sand less room to settle after a backwash.
Once I scooped some out, the problem stopped. If you’ve checked the valve and laterals already, it might be worth taking a peek at the sand level just to rule that out.
Once I scooped some out, the problem stopped. If you’ve checked the valve and laterals already, it might be worth taking a peek at the sand level just to rule that out.
Benjamin Tate
Member
A lot of good answers already, so I won’t repeat the gasket or lateral stuff. One other angle that gets overlooked is filter pressure and how dirty the sand bed was before you backwashed.
If you’re letting the filter run way past its normal clean pressure, the sand bed can get pretty compacted with gunk. When you finally backwash, it breaks loose unevenly. Then when you switch back to filter, a small burst of fines can sneak through before the bed fully re-sets, even if nothing is technically broken. I used to see a quick sand puff whenever my pressure had climbed 8–10 psi over clean.
What helped was backwashing a bit earlier and making sure the backwash itself was long enough. I wait until the sight glass runs clear plus another 20 seconds, then rinse for a full 30 seconds before going back to filter. Since doing that, no more sand fireworks on startup.
Also worth checking, do you hear air burping through the returns right after restart? Air rushing through can disturb the top of the sand bed and kick fines loose. Bleeding the filter slowly before full flow made a difference for me. Anyone else notice it’s worse after a really dirty pool or heavy vacuuming?
If you’re letting the filter run way past its normal clean pressure, the sand bed can get pretty compacted with gunk. When you finally backwash, it breaks loose unevenly. Then when you switch back to filter, a small burst of fines can sneak through before the bed fully re-sets, even if nothing is technically broken. I used to see a quick sand puff whenever my pressure had climbed 8–10 psi over clean.
What helped was backwashing a bit earlier and making sure the backwash itself was long enough. I wait until the sight glass runs clear plus another 20 seconds, then rinse for a full 30 seconds before going back to filter. Since doing that, no more sand fireworks on startup.
Also worth checking, do you hear air burping through the returns right after restart? Air rushing through can disturb the top of the sand bed and kick fines loose. Bleeding the filter slowly before full flow made a difference for me. Anyone else notice it’s worse after a really dirty pool or heavy vacuuming?
Brandon Hayes
Member
A lot of the big causes are already covered, so I’ll add one smaller thing that bit me once and drove me nuts.
Check the standpipe o-ring where it mates to the multiport. Mine wasn’t torn, just a little flattened and dry. Under normal filtering it was fine, but right after a backwash when flow and turbulence were high, a small amount of sand would sneak past for a few seconds. Looked exactly like a lateral issue, but everything inside the filter was intact. New o-ring and a light coat of lube fixed it instantly.
Also worth asking, does it only happen right after a vacuum-to-waste or a really heavy backwash? That’s when I noticed it most, especially if my clean pressure was already creeping 7–8 psi higher than normal. Curious if anyone else has seen the standpipe seal cause this kind of short sand puff.
Check the standpipe o-ring where it mates to the multiport. Mine wasn’t torn, just a little flattened and dry. Under normal filtering it was fine, but right after a backwash when flow and turbulence were high, a small amount of sand would sneak past for a few seconds. Looked exactly like a lateral issue, but everything inside the filter was intact. New o-ring and a light coat of lube fixed it instantly.
Also worth asking, does it only happen right after a vacuum-to-waste or a really heavy backwash? That’s when I noticed it most, especially if my clean pressure was already creeping 7–8 psi higher than normal. Curious if anyone else has seen the standpipe seal cause this kind of short sand puff.