Add the amount printed on your filter’s label or in its manual. For the common vertical-grid filters that is 3–9 lb of DE, depending on size: Hayward’s ProGrid filters take 3.0 lb (24 sq ft) up to 9.0 lb (72 sq ft), and Pentair’s FNS Plus filters take 3.6 lb (36 sq ft) up to 6 lb (60 sq ft). Add a full charge after every backwash or grid cleaning.
DE amounts by filter
| Filter area | Hayward ProGrid | Pentair FNS Plus |
|---|---|---|
| 24 sq ft | 3.0 lb (DE2420) | not listed in the 2025 guide |
| 36 sq ft | 4.5 lb (DE3620) | 3.6 lb (FNSP 36) |
| 48 sq ft | 6.0 lb (DE4820) | 4.8 lb (FNSP 48) |
| 60 sq ft | 7.5 lb (DE6020) | 6 lb (FNSP 60) |
| 72 sq ft | 9.0 lb (DE7220) | no 72 sq ft model |
The two makers ask for different amounts for the same area: a 48 sq ft Hayward takes 6.0 lb and a 48 sq ft Pentair takes 4.8 lb. So use your own filter’s number, not another brand’s chart. Hayward points you to the front page of the manual or to the filter label; DE is measured by weight, so weigh it or use a scoop you have checked on a scale.
How to add DE
- Protect your lungs and eyes. Pentair’s guide says: To avoid breathing dust, wear an NIOSH/ MSHA approved dust mask, as well as safety glasses to avoid dust contacting the eyes. Failure to properly handle diatomaceous earth could result in death or serious injury. Only use diatomite specifically marked for use with swimming pools and spas.
- Start the pump with the filter in normal FILTER position. When starting the system pump, Hayward says do not stand over or near the filter.
- Feed it through the skimmer. Pentair says to mix the required amount of diatomite with water in a bucket, then, with the pump running and skimmer valve open, pour the diatomite slurry directly into the skimmer. Hayward says to add it through the skimmer as fast as the plumbing will take it.
- Write down the clean pressure. Hayward says to record the pressure gauge reading after the D.E. has been added; that is your “pre-coat” or clean pressure.
Do not run the filter bare. Hayward says DO NOT operate the filter for more than a minute or two without the D.E. pre-coat, and Pentair says never operate it for longer than 3 minutes without diatomaceous earth because that will damage filter elements.
When to add more
- After every backwash. Backwash when the gauge reads 8–10 psi above the clean pressure (Hayward) or approximately 10 psi higher than the original starting pressure (Pentair). Hayward’s steps: backwash approximately two minutes, or until water out waste line appears clean, then add fresh D.E. as in the pre-coating step.
- After a grid cleaning, use the full charge again.
- Not as a top-up. If the pressure climbs back quickly after a fresh charge, see pool filter pressure high or low; grids that stay stiff after cleaning are covered in when to replace pool filter media.
Before you open the filter
A DE filter is a pressure vessel; Hayward lists a 50 psi maximum working pressure. Pentair’s safety tips warn that if air becomes trapped and is not released, it can compress and cause pressure to build, and that pressure may cause the lid to separate from the base. Before servicing, turn the pump off at the breaker, open the air relief valve, and stand clear of the filter and wait until all pressure is relieved; Pentair says the pressure gauge must read zero (0) psi. Spent DE goes out with the backwash water, and Pentair says to refer to local codes and ordinances for backwash, separation tank, and D.E. disposal.
For valve settings, see pool multiport valve positions. Choosing a filter type? Compare sand vs cartridge vs DE filters, or read the pool equipment and circulation guide. Sand filter owners need how much sand a pool filter needs instead.
Sources
- Hayward: ProGrid Vertical DE Filter Series Owner’s Manual (ISDE2423EF Rev E)
- Pentair: FNS Plus Vertical Grid D.E. Filter Installation and User’s Guide
- Pentair: 4 Safety Tips for Servicing Pool Filters
Research checked 2026-10-12.
