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How Much Diatomaceous Earth to Use in a Pool?

Swimming pool and pool house image by Jim Mills from

Diatomaceous earth (DE) consists of tiny fossils that have been ground into tiny pieces. Harvested from the bottom of the ocean floor, DE is capable of trapping dust and dirt particles much smaller than the human eye can see--down to 3 to 5 microns. This makes it one of the most effective filtering systems available for swimming pools. It can be difficult, however, to know exactly how much DE to place in the pool filter.

Filter Size

How much DE to use in a pool depends largely on the size of the pool and the pool filter. Smaller pools and filters need less DE, and larger pools and filters need more. The amount of DE to use also depends on how frequently your pool is backwashed and how dirty it gets. The average size of a DE pool filter is from 30 square feet to 60 square feet. The square footage of your pool equals the square feet of the filter. If you have a filter that is too small for your pool, it can overheat or filter at a reduced rate. A DE filter is able to filter out only as far as the label on the filter pump. You can use either a larger pump for larger pools or two different pumps on opposite sides of a pool.

DE Volume

A very simple formula determines how much DE to use in a pool filter at one time. For every 5 square feet of pool, 1 lb. of DE is needed in a pool filter. For example, a pool that is 30 square feet requires 6 lbs. of DE in the pool filter tank. If the pool filter cannot hold that much DE at one time, then fill it to capacity, unless your filter's manual states otherwise. The directions on a filter pump always should be followed, or the warranty may be voided or the system could malfunction.


Whenever the pump is backwashed, the DE level in the filter goes down. Because DE consists of tiny, ground fossils, it continues to break down and is released into the water. Some DE also is flushed through the waste line. When the amount of DE drops, the DE has to be replaced. It is helpful to mark the inside of the filter for future reference; when DE is first placed in the filter at the correct level, mark that level with a permanent marker. When the level of DE falls below that mark, add DE to the line. That way, you will always know how much DE is and should be in the filter.

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