Add DE to a cartridge filter system?

Jan 1, 2008
Las Vegas, NV
I have a pentair clean & Clear plus 420 (4 vertical cartridge) system and was wondering...the instruction manual says add .75 lb of DE into the skimmer for each 100 sq feet of cartridge surface, it will improve the filtration. I had been planning on adding 3 lbs of DE to the skimmer.

I just added new filters in NOV.

I went to the pool store and a fairly knowledgeable pool guy said not to do that, it would plug the filter...

What say you all?!


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May 7, 2007
Silver Spring, MD
Some cartridge filters will be destroyed the instant you add DE, others are fine. If your filter manual says that you can do it then go for it. If the manual doesn't specifically suggest it then better not to.


The DE is to be added only the first time the cart is used. It does plug up the cart a bit and help improve filtration butrepeated use will ruin the cartridge.