Strange pressure drop.

[uloset]

I recently opened the pool, unfortunately a week too late, so the water was not perfect, but it only took two quick doses of chlorine to pass the OCLT and bring my CC to .5. Anyway I have a mesh safety cover so tons of debris get though during the winter and it needed a good vacuuming. I really could not see to the bottom of the deep end so I started at the shallow side and my DE filter quick rose to 25psi, it normal sits around 14 PSI with a fresh load of DE. Just to make sure the pressure gauge is correct I always feel the returns and they were not flowing much at all. Usually I'll turn the filter off for a while and then after everything settles, the pressure sometimes drops slightly so I can get a little more vacuuming in.

Anyway I returned a while later and pressure was still at 25psi, but it was getting dark to I decided to backwash it the next day. I noticed a few leaves made their way through to the pumps basket, so I cleaned it out and also rinsed all my filter stockings out. The next day I turned the pump on and the filter was only reading 14psi, so I also tested my returns and they were flowing well, just like they always do at 14psi. Seemed a bit strange, but I figured perhaps some leaves made their way to the impeller, or even through to the filter before, but now had broken up and were not causing a clog anymore. Also it might have been a large load of dirt clogged the filter, but redistributed on the grids after being off all night. I still needed to filter the pool as I couldn't see the bottom of the deep end yet, so I continued to filter. Perhaps I'm just crazy because it is the beginning of the season, but the filter doesn't seem to be cleaning the water up as fast. I'm wondering what could be the problem, perhaps I blew a hole in one of my grids. I'll try vacuuming again and see if the dirt is coming out of the returns, but I'd also like to bounce this situation off all the pros here. Thanks in advance.

 

[Richard320]

Very likely you covered the grids with fine silt, which clogged them up and reduced flow and made the pressure rise. After it shut off, there was no more pressure holding things against the grids and the stuff slumped off. When it started again, the denser stuff settled on the bottom and the DE coated the grids and all was well. So far, so good.

Not cleaning the water is a worry. If you punctured a grid, you'd see a plume coming out the return. Although if your water is super cloudy, maybe not. It could be that the DE has gotten so loaded up that it's fallen off the grids and the water is going through uncoated areas.

Try backwashing. And when you're done loading the filter up with crud, do a full teardown and cleaning and inspect the grids.

 

[uloset]

Thanks for the info. The water is becoming clearer (I can see the bottom of the deep end now), but I'm not sure if that has more to do with the dead algae dropping to the bottom of the pool than the filter cleaning the water. The water was clear enough even at opening for me to clearly see the returns and I never noticed a plum, so hopefully all is well. I'll definitely be taking the filter apart soon to make sure the grids are in good shape.