Filtration & Circulation /
Why Is My Pool Filter Blowing Out Sand?
If sand is coming back through the returns, the sand filter likely has an internal failure or the valve is misdirecting flow. Shut the pump off and inspect safely.
Archive date: this article was written for PoolSkimmer on Oct 24, 2026 and given the earlier archive date of Oct 3, 2025 so the blog reads as an organized archive. It was not published on that date.
The problem with your pool filter blowing sand
When a pool filter is sending sand back into the water, it means the media has left the sand bed where it should be. This is typically down to an excess of sand in the tank, a faulty multiport valve, or damage to the standpipe or lateral. Before making any adjustments, be sure to heed the equipment manual and chemical labels, and never open the skimmer basket or filter access without first shutting off the pump.
Where to start your inspection
1. Make sure the pump is off. Do not inspect the skimmer or filter until you have confirmed this. 2. See how the valve handle is positioned. An improperly set multiport valve will let sand circumvent the filtration process. 3. Note the source of the sand. If it is coming out of the return jets, you are likely looking at an internal issue with the filter rather than surface debris. 4. Think about any recent work. Did the trouble begin after a repair or a backwash? That can be telling. 5. Use the pressure gauge as the manufacturer advises. Every setup has its own backwashing schedule.
Usual suspects for sand in the pool
For a sand filter to contain its media, the internal components must be sound. A failure in one of those parts allows sand to make its way to the return line and into the pool. You will often find the cause in:
- Laterals at the bottom of the filter that are loose or broken
- A vertical tube or standpipe with a crack
- Valve seals in the multiport, such as a worn spider gasket
- An internal assembly or tank that has cracked and will not seal
- Simply having too much sand in the filter for the proper bed height
Hayward’s own maintenance advice is to keep on top of routine care like cleaning the skimmer and to backwash per the maker’s instructions.
Is it the backwash?
It is normal to lose a little sand during a backwash, but if you see it being shot back into the pool, something is amiss. In most cases the backwash did not cause the problem; it merely revealed a pre-existing leak in the valve or a damaged lateral.
Some errors to steer clear of: running the pump with the valve in the wrong position, or assuming that sandy jets are a sign of bad sand. And do not open the filter with the pump still running.
Should you put off using the pool?
If sand is visible in the returns, the filter is not doing its job and the water quality will suffer. It is best not to operate it under those conditions. With the system off, there are a few things one can do safely: clean the skimmer basket, vacuum if the equipment permits, and brush the steps and walls to prevent dirt from settling. But if the water is cloudy, the pool is not ready for normal use.
Time to call in a pro?
A qualified technician can look over the return plumbing, valve and internal parts without the guesswork. Make a call if you are not at ease opening the filter yourself, or if you suspect a broken lateral or standpipe. Also get professional assistance if you spot electrical issues or leaks around the equipment. If the sand continues to blow in after you have double checked the valve setting, a technician is the way to go.
What to do next
The prudent course of action is to turn the pump off and have a look at the valve settings and the exterior of the filter. If the sand is still an issue, it will require a proper repair, not another rinse. Arrange for the fix.
Sources and further reading
- [Hayward: Weekly pool maintenance](https://www.hayward.com/maintenance/weekly-pool-maintenance)