How to Clean Your Pool Filter: Best Practices for Sand and D.E. Systems
Unlike cartridge filters that require you to manually remove and hose down the media, Sand and Diatomaceous Earth (D.E.) filters utilize a built-in mechanical cleaning process called backwashing. If you want to know how to clean your pool filter efficiently without wasting chemicals or water, mastering the backwash valve is essential. However, backwashing alone isn’t enough; both systems require periodic deep cleaning to maintain peak filtration.
The Mechanics of Backwashing
Normally, water flows from the top of the filter tank down through the sand or D.E. powder, trapping dirt along the way. Backwashing literally reverses this flow. Water shoots up from the bottom of the tank, lifting the sand bed or blowing the D.E. powder off the grids, and flushes the trapped dirt out through a dedicated waste line.
How to Backwash a Sand Filter
Wait until the pressure gauge reads 8 to 10 PSI over the clean starting pressure.
- Step 1: Turn off the pool pump. Never move the multiport valve handle while the pump is running.
- Step 2: Press down on the valve handle and turn it to ‘Backwash’.
- Step 3: Roll out your backwash hose to an area that can handle heavily chlorinated water.
- Step 4: Turn the pump on. Watch the clear sight glass on the valve. The water will run dark and dirty.
- Step 5: Run the pump for 2 to 4 minutes until the water in the sight glass is completely clear.
- Step 6: Turn the pump off. Move the valve to ‘Rinse’. Turn the pump on for 30 to 60 seconds. This resettles the sand bed so residual dirt doesn’t blow back into the pool.
- Step 7: Turn the pump off, move the valve back to ‘Filter’, and resume normal operation.
How to Backwash and Recharge a D.E. Filter
A D.E. filter requires the exact same 7-step backwashing process as a sand filter. However, there is one massive difference: when you backwash a D.E. filter, you are flushing the actual filtration powder out of the tank and into the yard.
Once you have finished the backwash and rinse cycle and returned the valve to ‘Filter’, you must immediately add fresh D.E. powder back into the system.
- Determine how much D.E. your filter requires (usually 1 lb of D.E. for every 10 square feet of filter area). Note: After backwashing, you only need to add about 80% of the full requirement, as some D.E. always remains on the grids.
- Mix the powder in a bucket of water to create a milky slurry.
- With the pump running, slowly pour the slurry directly into the skimmer. The pump will pull it into the tank and evenly coat the internal grids.
When Backwashing Isn’t Enough: Deep Cleaning
Backwashing removes loose dirt, but it does not remove heavy body oils, sunscreen, or calcium scale. Once or twice a year, both filter types require a deep clean.
- Sand Filters: Add a specialized liquid sand filter cleaner to the skimmer while backwashing, turn the pump off when the chemical hits the tank, let it soak for 24 hours, and then backwash the dissolved grease away.
- D.E. Filters: Once a year, the tank must be completely opened, the internal grid manifold removed, and the grids manually hosed off and soaked in a chemical degreaser to remove calcification and caked-on oils.
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