Amount of DE to add to Sand Filter


May 18, 2021
New Jersey
Pool Size
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-9)

I followed the instructions from Trouble Free Pool to add DE to my Hayward Sand Filter. I ended up adding 4 cups of DE but even then the PSI only went up about 1/2 - 3/4 PSI (hard to tell, only in increments of 1's). I decided to stop as the guide says it typically takes 1-2 cups of DE. My pool water looks clear (doesn't look like any DE was sent back in returns). I also watched my pump after adding the DE an saw the cloudy water come in and then clear up, so it appears as if the DE was sucked into the filter correctly.

I'll keep an eye on the PSI for the next 24 hours and see if I notice any change in water clarity but curious to know if others have had to add up and above 3 cups of DE to see a full PSI of pressure raise. Please note I am using a Pentair SuperFlo VS running at about 2300 RPM which pushes about 40/GPM in my setup. I did try a quick run at full 3450 RPM just to see if that made a difference but as expected it didn't. However I did notice my flow meter dropped a tad below 40 GPM after adding the 3 cups of DE and I had to bump the RPM up to 2350 to get it back to where it looked like prior to adding the DE so perhaps all is working as expected but wondering if I should add another cup or two of DE.

Jun 17, 2021
Please disregard my previous answer.
I believe the amount you need to add is dependent on the size of your filter which is why it is advised not to let the pressure build by more than 1 PSI rather than giving an exact amount to add. I would wait before adding more and check the pressure several times over the next 24 hrs. It is better to put in less than too much. If you didn't add enough you could always add more. If you put in too much you'll have to backflush and start all over again. Sorry for stating the obvious but it looks like you were just looking for a little moral support as I think you already knew the correct answer.
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