Complete Guide · 7 articles
DE Pool Filter Guide — How They Work, How to Maintain Them
DE (diatomaceous earth) filters provide the finest filtration available for residential pools — down to 2–5 microns vs 20–40 microns for sand. They require more maintenance than sand or cartridge filters, but the water clarity is unmatched. This guide covers everything from how DE filters work to grid cleaning, DE powder quantities, and troubleshooting.
Pool Filter Guide Editorial Team
4 FAQs answered
Updated 2025-04-14
All Guides in This Section
7 articles Guide 01
What Is a DE Pool Filter? How diatomaceous earth filters work and why they filter finest.
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How-To 02
How to Backwash a DE Filter DE backwash is different - you must re-add DE powder after every backwash.
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How-To 03
How Much DE for Pool Filter? DE powder quantity by filter size - and how to add it correctly.
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How-To 04
How to Clean a DE Pool Filter Backwash routine plus full annual grid service - the step most owners skip.
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How-To 05
DE Pool Filter Grids How to clean, inspect, and replace DE filter grids.
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Review 06
Best DE Pool Filter Pentair FNS Plus vs Hayward Pro-Grid - DE filters ranked on clarity, maintenance burden, and build quality.
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Comparison 07
DE vs Sand vs Cartridge Filter Side-by-side comparison: filtration quality, cost, maintenance.
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Diatomaceous earth powder, DE grids, and filter cleaner
Frequently Asked Questions
What is a DE pool filter?
A DE (diatomaceous earth) pool filter uses a fine powder made from fossilized algae (diatoms) coated on filter grids to trap particles as small as 2–5 microns — the finest filtration of any pool filter type. The DE powder is the actual filtering medium, not the grids themselves. After each backwash, you must add fresh DE powder to re-coat the grids.
How much DE do you add after backwashing?
After backwashing, you replace approximately 80% of the filter's rated DE capacity. A 48 sq ft filter (a common residential size) holds about 6 lbs of DE total, so you would add roughly 4.8 lbs (just under 1 lb per 10 sq ft of filter area). Mix the DE with water in a bucket first to form a slurry, then pour it into the skimmer with the pump running.
How do you clean DE filter grids?
To deep-clean DE filter grids: (1) Backwash the filter. (2) Turn off the pump and release pressure. (3) Remove the filter lid and carefully pull out the grid assembly. (4) Soak the grids in a filter cleaning solution for several hours or overnight. (5) Rinse each grid thoroughly. (6) Inspect for tears — even a pinhole will cause DE to pass into the pool. (7) Reassemble and add fresh DE.
Why is DE powder getting into my pool?
DE in your pool water means DE is bypassing the grids — typically caused by a torn or damaged filter grid. Even a small pinhole allows DE to return through the return jets. To diagnose: backwash, add fresh DE, and watch for cloudy white water coming from the jets. If you see it, disassemble and inspect every grid carefully. Replace any grid with visible damage.