Things You'll Need
Diatomaceous earth (DE) is a powder that coats the grid inside a pool pump. Although DE powder is used for filter grids, it can be added to sand filters. When the powder is added to the sand, the sharp edges of the DE powder enhance the filtering process of the sand by capturing tiny dirt particles during the filtering process. The powder is added to the pool filter after back-washing or before starting up the pool after it has been closed for the winter.
Back-wash the sand filter. Note the pounds per square inch (psi) on the pressure gauge on the pump. Turn the pump on so it is filtering.
Pour water into the one-gallon bucket, stopping one inch from the top.
Measure out 1/4 cup of diatomaceous earth. Pour the DE powder into the bucket of water.
Remove the cover from the skimmer. If you use a skimmer sock, remove the sock from the skimmer. Turn on the pump so it is filtering the water. Slowly pour the DE solution into the skimmer. Replace the skimmer cover. Wait for three minutes.
Check the pressure gauge. When adding DE powder to a sand filter, you want the psi to raise by one. For instance, if your clean reading after back-washing is 4 psi, the reading after adding DE should rise to 5 psi.
Repeat steps 2 to 4 until the pressure gauge reads 1 psi higher than the clean reading. It may take one to two cups of DE powder, but when adding this powder to a sand filter for the first time, only use 1/4 cup at a time. Any time after the first initial successful use of DE powder in the sand filter, you can add the total amount of powder at one time.
Check the pressure gauge for the next 24 hours. The filtering process may capture more dirt particles after the DE powder has been added and require back-washing to lower the psi reading.