Pump problem with DE filter

[bsnelson]

Apologies for the vague subject, but my problem doesn't really condense to a one liner very well.

I've got a several year old 2 or 2.5 HP single speed pump, mated to a less than 1 year old Pentair FNSP60 DE filter. I previously had a sand filter, which was very forgiving of my sometimes lax maintenance. I tend to let some green in, especially when it's early spring but still too cold to swim.

I realized quickly that the DE filter will clog quicker and need flushing, but lately, I've had an odd problem: within a day or two of flushing/recharging, I'll see that the water isn't flowing after the pump has been running for some time. When I go to the pump, it's almost like it's cavitating. There's water in the filter basket area on the pump, but there's air , too, and they're just swirling around, but not really flowing. Filter pressure gauge reads very low (less than 10 lbs).

At this point, I can stop the pump wait a few minutes, then restart, at which time it will resume good flow. Filter gauge reads anywhere from 23 to 26 psi or so (fresh charge baseline is 20). After an hour or less, we're back to the light/no flow.

Any ideas? I swear I don't remember this behavior last year, seems like it'd keep going with progressively less flow until about 30 psi, at which point I'd flush and recharge. Maybe my impeller is having a problem?

Brad

 

[JVTrain]

Have you taken the filter apart to completely clean the grids recently?

 

[Richard320]

Apologies for the vague subject, but my problem doesn't really condense to a one liner very well.

I've got a several year old 2 or 2.5 HP single speed pump, mated to a less than 1 year old Pentair FNSP60 DE filter. I previously had a sand filter, which was very forgiving of my sometimes lax maintenance. I tend to let some green in, especially when it's early spring but still too cold to swim.

I realized quickly that the DE filter will clog quicker and need flushing, but lately, I've had an odd problem: within a day or two of flushing/recharging, I'll see that the water isn't flowing after the pump has been running for some time. When I go to the pump, it's almost like it's cavitating. There's water in the filter basket area on the pump, but there's air , too, and they're just swirling around, but not really flowing. Filter pressure gauge reads very low (less than 10 lbs).

At this point, I can stop the pump wait a few minutes, then restart, at which time it will resume good flow. Filter gauge reads anywhere from 23 to 26 psi or so (fresh charge baseline is 20). After an hour or less, we're back to the light/no flow.

Any ideas? I swear I don't remember this behavior last year, seems like it'd keep going with progressively less flow until about 30 psi, at which point I'd flush and recharge. Maybe my impeller is having a problem?

Brad

Air in the pump basket and low pressure are symptomatic of a suction-side air leak. It could be as simple as low water level. After a period of time, a vortex is created in the skimmer and you start sucking air. Once you shut it off, the vortex goes away, and then the pump will prime and flow nicely again until the vortex reappears.

 

[bsnelson]

Have you taken the filter apart to completely clean the grids recently?

Have not yet done that, it's probably time.

Brad

 

[bsnelson]

Putting a bow on this: In what has to be one of the most blatant examples of "try the easy things first": Richard320 called it, the root cause was a poor seal on the pump housing cover (trap cover). It occurred to me to check that part for cracks, and when I took it off, I noticed that there was some sand and other small debris in the area of the O-ring. I cleaned the O-ring and all of the sealing surfaces well, put it all back together and it's run for a number of hours with absolutely no air under the cover and no cavitating.

I did, however, verify that the cover does have cracks, by turning the lid over, filling it with water and watching for drips (which did appear). So, I'm replacing the lid, O-ring and trap basket (the latter has some chips missing from the top).

I had already cleaned the grids and recharged (thanks for that suggestion, JVTrain), and that didn't fix the problem.

Thanks, all!

Brad