Confused about DE - why, when, how?


Well-known member
Jun 3, 2015
I don’t really understand what DE is, what motivates pool owners to use it, and how I determine when to use it? It appears there are dedicated DE filters, but there also seems to be another group of DE users that simply add it to their skimmer so it gets trapped in the sand filter.


TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
Key West, FL
On occasion, with a sand filter, you can create a slurry with about 1/2 cup of DE and water, and pour into the skimmer. This causes a find layer of DE on the sand to trap smaller particles, and can help getting rid of residual cloudiness after a SLAM.

DE is Diatomaceous Earth, crushed fossils. Its a white powder that looks like fine flour.


LifeTime Supporter
TFP Guide
Jan 18, 2015
Bunbury, WA, Australia
Some enjoy the more polished look when they add DE to the sand filter.

However, the obvious downside is more frequent backwashing as it will catch finer debris- then its the cost of draining/refilling not to mention adding salt, CYA and other possible adjustments to the water balance.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
Looking at it through a microscope, DE looks a bit like kitchen sponges. Google some images and check it out. It's pretty neat.

Anyway, picture a screen made of chicken wire. The tear up up a bunch of sponges and spread them across the screen. Now pour water on it. The water will have to go through the holes on the sponges. That's a DE filter.

Adding the DE to a sand filter just exchanges the frame for a layer of sand.