Domakihub How to Backwash a Pool Sand Filter the Right Way
Know the pressure reading that triggers a backwash, the exact valve sequence, and how often Greek pools need it.
Reviewed by Domakihub pool pros Β· 2026-06-23 Β· 5 min read
Backwashing is one of the most routine tasks for any pool owner in Greece, yet skipping it β or doing it wrong β leads to cloudy water, overworked pumps, and shortened filter life. The video above walks through the full process visually; the steps below give you the exact sequence and the pressure numbers to watch so you always know when to act. Whether you manage a private villa, a holiday rental, or a hotel pool on one of the islands, this guide applies to every standard sand filter system.
Why Pressure Is the Only Trigger That Matters
Your sand filter has a pressure gauge on top of the tank. When the filter is clean and operating normally, that gauge will show a baseline reading β typically between 8 and 12 PSI depending on your pump and plumbing. Write that number down the first time your filter runs clean after a full backwash and rinse. That is your baseline.
The rule is straightforward: once the gauge climbs 8 to 10 PSI above that baseline, it is time to backwash. At that point the sand bed is loaded with debris and water is being pushed through with more force than the pump was designed to handle. Do not wait until the pressure is 15 PSI over baseline β the extra strain shortens the life of both the pump and the filter media.
The Greek Swim Season Changes the Frequency
In northern Europe a sand filter might need backwashing every two to four weeks. In Greece the equation is very different. The Aegean swim season runs from late April through October β sometimes longer in Crete and the Dodecanese β and pools are under almost daily bather load during the summer months. Add the Saharan dust that settles across southern Greece every spring, plus the pollen load and the fine particles that sea breezes carry, and a busy pool can reach that trigger pressure in as little as five to seven days at peak season.
During the off-season or when a pool sits unused for a stretch, pressure rises more slowly. Check the gauge at least once a week regardless of use. A pool that looks clear but reads high pressure is still forcing water through a dirty bed, which means the filter is no longer doing its job properly.
Step-by-Step: The Correct Backwash Sequence
- 1
Turn the pump off completely
Never move the multiport valve handle while the pump is running. Switching valve positions under pressure can crack the spider gasket inside the valve β a repair that costs far more than a few seconds of patience. Flip the pump switch off, wait for the impeller to stop, then proceed.
- 2
Set the valve to BACKWASH and run for two to three minutes
Rotate the multiport handle to the BACKWASH position. Turn the pump back on. Water now flows backward up through the sand bed, lifting trapped debris and flushing it out through the waste line. Watch the sight glass or waste hose: the water will start murky and brown. Run the pump until the water running to waste turns clear β usually two to three minutes. If your pool has heavy algae or you have just shocked it, let it run for a full three minutes even if the water clears sooner.
- 3
Turn the pump off, switch to RINSE, and run for thirty seconds
The rinse step is skipped far too often, and it causes most of the cloudiness complaints after a backwash. After the backwash cycle, turn the pump off again, move the handle to RINSE, then restart the pump for thirty seconds. Rinsing re-settles the sand bed and flushes any remaining loose debris to waste before you send water back into the pool. Without this step, the first water returning to the pool will be cloudy.
- 4
Turn the pump off and return the valve to FILTER
Once the rinse is done, turn the pump off one more time, rotate the handle back to FILTER, and restart the pump. Check the pressure gauge immediately β it should now read at or very close to your clean baseline. If it is still elevated by more than 2 PSI, the sand bed may be channelled or the filter may need a deep clean with a sand filter cleaner product.
- 5
Top up the pool and log the date and pressure
A thorough backwash sends roughly 200 to 500 litres of water to waste depending on your tank size, so check the water level and add fresh water if needed. Jot down today's date and your post-backwash baseline pressure β this log takes thirty seconds and tells you exactly when the next backwash is due. For hotel and rental pools, make this entry in the maintenance log that technicians and property managers can both access.
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FAQ
- How often should I backwash my pool sand filter in Greece during summer?
- Check the pressure gauge at least once a week. In a busy Greek pool during July and August β heavy bather load, Saharan dust, and sea pollen β the trigger pressure (8 to 10 PSI above your clean baseline) can be reached in five to seven days. During spring and autumn with lighter use, every ten to fourteen days is more typical. Always go by the gauge rather than a fixed schedule.
- Can I backwash too often?
- Yes. Every backwash sends pool water and the chemicals dissolved in it to waste, and it also slightly disturbs the sand bed. Backwashing too frequently β before pressure actually rises β wastes water and chemicals without any real benefit. The sand filter actually works better when the bed has a light coating of trapped particles, because that layer helps catch finer debris. Only backwash when the pressure tells you to.
- My pressure drops back to baseline after backwashing, but the pool water is still cloudy. What is wrong?
- Cloudy water after a successful backwash usually means one of three things: you skipped the rinse step and loose debris returned to the pool; your sand is old and channelled (sand should be replaced every five to seven years); or there is a separate chemistry issue such as low chlorine, high pH, or a recent algae bloom. Check your chemical levels first, and make sure you always run the RINSE cycle after every backwash.