Low to Zero Pressure in Filter

Hello - I recently had a problem with my pump not priming fully and had zero pressure in my filter. I was able to clear out some junk from the impeller, cleaned out all the baskets and my filter as well. After putting everything back together the pump runs fully primed but the filter is still almost at zero. I also got a new pressure gauge. I have good flow coming from the returns and everything "looks" good overall.

Should I be concerned about the low pressure?

Thanks in advance!

Perhaps the pressure gauge is shot?

Dave, that was my thought, too. A pressure gauge can be replaced easily and inexpensively. I think I'd try that first.

I put a new pressure gauge on as well.

Could you tell us more about the piping, pump, filter and any other attached gear?

I have a 48 sq ft pentair FNS plus filter, 1 HP one speed pump (not sure of brand), all PVC pipes. Also I have a Polaris booster pump that drives a Polaris 280.

Thanks

Have you inspected the grids to verify they're not damaged? There isn't a valve set to bypass on it, is there?

kelemvor - I think some of the grids are definitely damaged. I didn't see any tears or holes but the inside manifolds (right term?) on several of them were broken or moved around a little. Needless to say, I've ordered a new set of grids. Stupid question - but exactly how would that affect the filter pressure?

Thanks again for your responses - I appreciate it!

Blocked or damaged grids would probably raise the filter pressure. But when the pump is running can you feel any flow out of the returns? Do you have a check valves on the suction side of the plumbing?

Yes there is flow from all the returns. And no I do not have any check valves.

If you are feeling "strong" flow from the returns and your filter pressure is close to 0, then there are only two possible explanations.

1) You are running on low speed of a VS or two speed pump that you failed to mention. This is normal.

2) There is still something wrong with the pressure gauge.

Thanks, Mark. I am definitely running a 1 sp / 1HP pump. Since I replaced the pressure gauge, I guess I'll replace the release valve too. (The gauge screws in to the top of the valve on my filter.)

One thing I did fail to mention is that I have an attached heater. I've never used it so I sometimes forget it's there. Would anything there be a possible cause?

No, the heater would not cause that problem. Heaters cause filter pressure to rise, not fall.

If you are feeling strong flow out of the returns, then it is most likely something to do with the pressure gauge and/or location of it.

Here's a crazy idea: Could the passage to the pressure valve be partially blocked? If so, it would read low pressure, even with a new valve, yet the pressure at the returns would "feel" normal.

remove pressure gauge and turn on pump an make sure there is flow out of PS hole it could just be plugged