DE filter pressure up at night and back to 'normal' in the morning

[tbenton]

Opened pool 4 days ago for the season here in Virginia. Water is clear but 'dirt' on bottom. Had pool since 1987 so am used to this and it takes a few days for it all to go away with daily brushing/filtering. I brush and after many hours the pressure starts to go up and when it gets to 21-22 in the evening I shut it down and know its time to backwash next morning but in the morning pressure is back down to normal reading of 11 and does not go back up unless I brush it and even then it takes many hours to start going up. This has happened every year when getting rid of the 'dirt' upon opening so thought it was time to ask about it. Just wondered why it goes back down and if this is harmful to the filter process?

 

[Richard320]

Probably everything on the grids falls off when the pump is off. When you start it again, the DE recoats the grids while the heavier stuff like sand settles to the bottom.

 

[tbenton]

Probably everything on the grids falls off when the pump is off. When you start it again, the DE recoats the grids while the heavier stuff like sand settles to the bottom.

---Thanks Richard! It actually is a good thing as long as its not harming the filter process because I don't have to backwash every day after brushing but will backwash tomorrow and it will be interesting to see how dirty it is. We call the dirt on the bottom 'fluff'. It has little consistency. Can't use robotic cleaner yet because they don't like cold water....needs to be over 60°. Should be ok to put it in tomorrow I hope.