clarifier use


Aug 9, 2007
Still battling my large cloudy pool! The pool store "professional" said NEVER use clarifier in a pool with a DE filter, it gunks up the filter. Is this true?


Mod Squad
TFP Expert
Apr 4, 2007
SW Indiana
I can't see any reason to use it. If your filter isn't needing backwashing fairly often with dirty water, you may have a filter problem.


Aug 9, 2007
I have used clarifier before with no problems. It did a great job of dropping any real tiny particles to the floor quickly; making it easy for a quick vacuum. My question still is, does it "gunk up" the DE filter? The clarifies has no such warnings! Thanks for everyone's help. Priceless!!!


TFP Expert
Platinum Supporter
LifeTime Supporter
May 7, 2007
Silver Spring, MD
Clarifier won't have any long term impact on a DE filter. They can sometimes lead to a day of frequent bumping/backwashing, but the water clears up quickly, the bumping/backwashing ends, and everything is fine again.

Clarifier causes small particles, ones so small that they pass right through the filter, to clump together into larger particles which the filter can trap. If you are in a situation where clarifier is required (very rare by the way) then adding clarifier would result in a sudden and large increase in the amount of stuff that the DE filter catches. In some cases that could lead to a very frequent need to bump/backwash the DE filter for several hours to a day, as it suddenly becomes able to filter out the newly clumped together particles. Once that period ends everything is back to normal with no damage done.


Well-known member
Jun 5, 2008
DE filters can remove particles as small as 1 micron (as opposed to sand which removes particles as small as 40 microns). Hence, it's rarely necessary to add clarifier if you have a DE filter, as the filter is probably already going to remove the particles as they are.

If you DO gunk up a DE filter, it will sometimes mean replacing the DE and cleaning out the filter, but it shouldn't damage it permanently. You should watch the pressure and bump as necessary, and if it goes right back up, clean it out and replace the DE.

I've never had to use a clarifier in my DE filtered pool. The filter is able to remove very small particles and keeps the water very clear. Clarifiers are of more use for those with sand or cartridge filters that cannot remove the particles until they are made larger by the clarifier.


Correction, DE filters will filter to about 6-10 microns in actual pratice, carts aabout 20 microns and sand about 60 microns. Both sand and carts filter better when slightly dirty. DE will develop a lot of back pressure when dirty. The probelm with using polymeriic clarifiers with DE filters is that that they will essentially clog the filter and require breaking it down and cleaning it. Backwashing or bumping won't really be effective.