Swimming pool filter pressure gauge suddenly showed abnormal pressure drop from 27psi to below 10 psi. Swimming pool fountain features also noticeably lost pressure. Pump was running louder than usual. No visible leaks.

So before calling specialist I decided to remove filter basket and check if something is stuck in impeller:

enter image description here

enter image description here

I have cleaned filter basket couple times and have never paid attention to what I believe to be diffuser (part # R0445305) to be sticking out like that in housing. Is it normal? Could it be the culprit for low pressure?

Model number is centurion 193995xcn.

Update#1 in response to comments

Here is picture with model number visible:

enter image description here

The housing was full with water and there was no air at all. I believe this proves that pipes on the pump's intake side are not cracked and are not pulling in air, right?

The main drain and two skimmer pipes join together just before the pump. Since I have operated pool with just one skimmer on (when suction vacuuming pool) without such noticeable pressure drop, then would this prove that pump's pipes on intake side are not clogged?

If any of pipes on pump outlet side were blocked then the pressure at the filter should be unusually high and not low, right?

  • Are you sure about the diffuser part number? Googling that gives me one that doesn't look anything like yours (smooth cone taper instead of the step seen in your photos). Also, the symptoms you describe are typical for a suction side issue (blockage or air leak). Does the pump prime normally? Is the basket full of water when running or do you see significant air? When you turn the pump off, does water rush back through the basket into the suction line? You can also try to take the basket lid off while the pump is running to see how much vacuum there is on the suction side.
    – TooTea
    Commented Jan 14, 2022 at 8:31
  • Also, what kind of noise does the pump make? Is it more like gurgling (cavitation) or a grinding/whining (mechanical) noise? If you have a valve on the suction line, try closing that (to induce cavitation) and see how the pump responds.
    – TooTea
    Commented Jan 14, 2022 at 8:35
  • I don't see anything abnormal, that looks to be the screw that holds the impeller in place. I'm no expert, but you may have a broken seal behind that. I just had to replace my motor because the seal was leaking resulting in loss of pressure and pump losing prime. Remove the motor and disassemble the whole unit in front of it to find the issue. Likely, shaft seal and/or other gaskets there. OR, 1 - you could have an air leak prior to the motor, 2 - the basket gasket. Commented Jan 14, 2022 at 13:44
  • You seem to know the make/model number of the filter and even the part number for the piece in question. When you were looking all those up, did you find any pictures/drawings of how it was all supposed to go together? If so, you've probably got a better idea than we do. If you're still not sure, maybe include a link to the pictures/drawings and somebody else may be able to interpret them better.
    – FreeMan
    Commented Jan 14, 2022 at 14:46
  • @TooTea You are right. I checked again and the diffuser part is actually R0445305. My pump is below swimming pool water line so I believe I should not remove the lid unless the suction side valves are closed and pump is off, right? Otherwise water will gush out. Commented Jan 17, 2022 at 1:39

1 Answer 1


Just disassembled unit and the diffuser had broken into two pieces.

So, if after removing filter basket you notice the diffuser "mouth" appears to be misaligned as in my picture then most likely diffuser is bad as it is supposed to be held by two screws on both sides to backplate.

Also, there seems to be design problem with Jandy as those screws often come loose allowing diffuser to move freely (at least this is what I found in replacement part comment section). I think I found my screws in water filter long time ago, but at that time did not realize what they were.

enter image description here

  • wonders if the bounty can be awarded to a self answer...
    – FreeMan
    Commented Jan 18, 2022 at 15:42

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