Adding DE filter powder is a routine maintenance step — necessary after every backwash, after a filter clean, and whenever filter pressure drops below the clean baseline (which means DE has washed out). Done right, it’s a 5-minute job that restores filtration to factory performance. Done wrong, you end up with DE in the pool, clogged returns, or a damaged filter.
How much DE to add
Every DE filter has a rated DE capacity printed inside the housing or on the manufacturer’s label:
- 24 sq ft filter: 3 lb of DE
- 36 sq ft filter: 4.5 lb
- 48 sq ft filter: 6 lb
- 60 sq ft filter: 7.5 lb
- 72 sq ft filter: 9 lb
Rule of thumb: 1.25 lb of DE per 10 sq ft of filter area. Always check your specific filter’s spec — overdosing causes high pressure and short filter cycles; underdosing means DE doesn’t fully coat the grids and you get cloudy water.
What you’ll need
- Fresh DE powder (food-grade or pool-grade silica-based)
- A measuring scoop or kitchen scale (most DE comes with a scoop)
- A 5-gallon bucket
- A dust mask (DE is a fine inhalable powder)
- Water
Step-by-step
DE goes in through the skimmer with the pump running and the multiport on Filter. Confirm before mixing anything.
Use the chart above or your filter’s spec sheet. Never guess — even a 25% overdose will cause measurable backpressure problems.
Fill a 5-gallon bucket about 2/3 with water. Slowly stir in the DE while pouring — never dump the DE in dry. You’re aiming for a smooth, milky-thin slurry without dry clumps.
With the pump running, pour the slurry into the open skimmer over 30–60 seconds. The DE flows through the suction line, into the pump, through the multiport, and coats the grids. You’ll see pressure rise as the DE seats on the grids.
Pressure should rise 2–4 PSI as the DE settles. If it rises 8+ PSI, you over-charged — back-flush briefly and try again with less DE next time. If it doesn’t rise at all, the DE went through the grids (likely a torn grid) and is now in your pool.
Look at the pool returns within 60 seconds of adding the slurry. If you see grey-white powder coming back into the pool, you have a torn grid, broken manifold, or missing standpipe cap. Shut off the pump and inspect.
What kind of DE to buy
Two kinds are sold: pool-grade DE (calcined diatomaceous earth, heat-treated for use in filters) and food-grade DE (not heat-treated, sold for pest control). Pool filters need pool-grade. Food-grade has different particle size and won’t coat the grids properly.
50 lb bags are the standard residential purchase size and last 6–12 months for a typical pool with monthly backwash cycles.
DE filter parts in stock
Hayward 22″ DE Retainer Rod
$78.10
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0–60 PSI Pressure Gauge
$13.50
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Multiport Spider Gasket
$34.80
Shop NowIf you keep adding DE and pressure never rises, you have a torn grid. Send PST Pool Supplies a photo of the grid assembly and we’ll match replacement grids for your filter model.