Low pressure/ High flow after cleanout because DE in pool.

Hi all,
I was getting some DE back into the pool, so I just completed my first deep filter clean since inheriting the pool. After close inspection during the clean, there are no cracks in the top manifold and the grids look to be in good shape although they were filthy - this may be normal?? (the grids are about 5 years old from when the pool was built).
I believe all went well during the clean. I purposefully reloaded with a little less DE than recommended (only 37 cups of DE for a 48 sq inch filter) because I think I may have had too much DE after the last time I backwashed - since that seems to be the only reason left why I might have been getting DE in the pool.
Now that I am finished, and reloaded the DE, after an hour I noticed that my pressure gauge reads lower, (6 instead of 10), and the intake/return jets in the pool are MUCH stronger. Is this a result of the clean filters, and reloading with a little less DE?
If I still am getting DE back in the pool tomorrow - what could cause that?
Any assurance/ feedback/ suggestions are welcome.


Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
Bedford, TX

Yes... Filter pressure is the amount of effort it takes to force water through the filter.. It take less effort to force water through a clean filter, so you have a lower pressure.. My filter pressure is about 1 PSI...

While you might get a little DE back in the pool when clean, it should not be much or for as long..

The only way DE gets back to the pool is by by-passing the filter grids.. Usually this is because of missing O-Ring, damaged grids or a cracked manifold.

I suggest that you add the full recommended amount when the grids are clean and about 80% after you backwash..


Jim R.
  • Like
Reactions: StupendousMan


Gold Supporter
If you inspect the fabric over the grids, any rip, tear or hole will allow DE to pass through. Its amazing how small a hole can pass so much. BTW your filter pressure is your indicator of when its time to clean again. Remember that pressure (6 psi) and when the pressure is up to 25% over your clean pressure its time to clean.. so at 10psi, you were overdue. In case you haven't see this from the wiki:
  • Like
Reactions: StupendousMan