Would appreciate any suggestions for weak suction and corresponding weak pressure in return lines but normal/stable PSI at filter and no apparent air in the system. Equipment pad is in garage, approximately 10 feet vertically below pool surface level and 30 feet away horizontally. Pool is four years old, there have never been any suction side or pressure side flow issues, so this is new. Pool and equipment as described in my signature line below. Normal PSI at filter is 12 with pump running at 1800 rpm, 15 at 2000 rpm, 20 at 2500rpm and 30 at 3500 rpm. I have cleaned the cartridges multiple times, ensured that pump lid and filter lid and their O-rings are well sealed. Priming the pump is never a problem given the gravity. There are no air bubbles in pump or coming out of returns. It is a one skimmer pool, with main drains plumbed to the other port in the skimmer box.
Pump is set to run main shift at 2000 rpm. It begins working normally, regular flow to/from pool, but after 30 minutes or an hour the flow weakens considerably until even the SWG turns off for lack of flow, but PSI remains the same. What would cause this? I can increase pump rpm to 2500 or 3000 and flow will increase and SWG will turn back on, at least temporarily, but this raises PSI in system considerably and doesn't seem like a permanent solution. It makes no difference whether heater loop you can see in the picture at right is turned on or off. Pool water is clear, chemicals normal (maybe PH a bit low at the moment).
* Note that the skimmer ports seem to have been plumbed in reverse, meaning that the main drain lines seems to have been connected to the port at the back of the skimmer, furthest from the pool, and the main suction line seems to be the port closest to the pool. Not sure how/why this was done or whether it makes a difference, but this setup has not caused any flow issues since installation past three years so perhaps not relevant for purposes of this discussion.
Pump is set to run main shift at 2000 rpm. It begins working normally, regular flow to/from pool, but after 30 minutes or an hour the flow weakens considerably until even the SWG turns off for lack of flow, but PSI remains the same. What would cause this? I can increase pump rpm to 2500 or 3000 and flow will increase and SWG will turn back on, at least temporarily, but this raises PSI in system considerably and doesn't seem like a permanent solution. It makes no difference whether heater loop you can see in the picture at right is turned on or off. Pool water is clear, chemicals normal (maybe PH a bit low at the moment).
* Note that the skimmer ports seem to have been plumbed in reverse, meaning that the main drain lines seems to have been connected to the port at the back of the skimmer, furthest from the pool, and the main suction line seems to be the port closest to the pool. Not sure how/why this was done or whether it makes a difference, but this setup has not caused any flow issues since installation past three years so perhaps not relevant for purposes of this discussion.
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