Because of their ability to clean the smallest of particles from pool water, diatomaceous earth (DE) pool filters are favored by pool owners with allergies or children who are sensitive to dust and pollen. With the ability to filter out particles as small as 2 microns in size, which is smaller than the naked eye can see, diatomaceous earth filters produce the cleanest and clearest filtered pool water. The trick with this type of filter is adding the appropriate amount of DE.
Clean the filter before adding the DE. Diatomaceous earth will not stick properly to dirty filter elements. Oils and minerals found in pool water make it difficult for the DE to stick.
Turn the filter on and watch the water entering the pool at the return. If there are a lot of bubbles in the return water, wait until all the air is out of the filter and the bubbles cease. Pool filters must operate in an airtight vacuum environment.
Put on a protective mask. The fine particles in diatomaceous earth love sticking to anything that's moist. If you inhale diatomaceous earth, it will stick to the lining of your lungs. Unfortunately, you cannot wash the DE out of your lungs; therefore, you must take precautions not to inhale it.
Review the manufacturer's instructions for the amount of DE to add. Filter models differ; some require as little as 2 pounds while others require as much as 9 pounds of DE. If you don't add enough diatomaceous earth, the filter won't clean the pool properly. If you add too much, you'll find your DE on the bottom of the pool.
Slowly pour the diatomaceous earth into the skimmer. If you pour in large clumps of diatomaceous earth at one time, it will bypass the filter and end up in the pool. Shake it into the skimmer slowly. Watch it as it goes past the pool pump basket. Once you no longer see the DE cloud in the pool pump basket, you can add a little more.
Check the pool return for evidence of diatomaceous earth. If you're adding it at the right rate, you won't see evidence of it returning into the pool.