Complete Guide · 7 articles
How to Backwash a Pool Filter — Sand, DE & Cartridge
Backwashing reverses water flow through your filter to flush trapped debris out the waste line. It is the most routine pool filter maintenance task — but the most commonly done wrong. This pillar covers the correct procedure, the right frequency, and brand-specific steps for every major filter manufacturer.
Pool Filter Guide Editorial Team
4 FAQs answered
Updated 2025-04-14
All Guides in This Section
7 articles How-To 01
How to Backwash a Pool Filter The complete backwash procedure - step by step for sand and DE filters.
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How-To 02
How to Backwash a Hayward Pool Filter Model-specific steps for Hayward ProSeries and PowerFlo filters.
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How-To 03
How to Backwash a DE Pool Filter DE filter backwash is different - includes replenishing DE powder after.
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How-To 04
How to Backwash a Pentair Pool Filter Triton II and FNS model-specific steps and DE recharge amounts.
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Guide 05
What Does Recirculate Do on a Pool Filter? Recirculate bypasses the filter - when it is useful and when to avoid it.
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Guide 06
How Often to Backwash Pool Filter The PSI rise rule - why calendar schedules are wrong.
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Guide 07
Pool Filter Valve Settings Guide Filter, Backwash, Rinse, Waste, Recirculate - when to use each position.
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Frequently Asked Questions
How do you backwash a pool filter?
To backwash a sand or DE filter: (1) Turn off the pool pump. (2) Set the multiport valve to BACKWASH. (3) Turn the pump back on and run for 2–3 minutes or until the water in the sight glass runs clear. (4) Turn the pump off, set the valve to RINSE, and run for 30 seconds to re-settle the sand. (5) Return the valve to FILTER and resume normal operation. Never move the multiport valve while the pump is running — you will crack the valve body.
How often should you backwash a pool filter?
Backwash when your filter pressure gauge reads 8–10 PSI above your clean baseline reading (the PSI right after your last backwash). The common "backwash every week" advice is wrong — a filter is actually most efficient when slightly loaded. Backwashing too frequently removes the debris cake that helps trap finer particles.
How long should you backwash a pool filter?
Run the backwash cycle until the water in the sight glass (the small indicator on your multiport valve) runs completely clear. This typically takes 2–3 minutes. After backwashing, always run the RINSE cycle for 30 seconds to re-settle the filter media before returning to the FILTER position.
Should I backwash after shocking my pool?
No. Run your filter for at least 24 hours after shocking before backwashing. Shocking raises chlorine levels to kill algae and bacteria, and the filter actively traps the dead organic material during this period. Backwashing immediately after shocking removes that trapped material before it can be collected, reducing the shock's effectiveness.