Low system pressure

Hi.

Since a few weeks I am battling low pressure in my pool system. At times, the pool pump can't even get over the priming cycle (Sta Rite Variable Speed, 2-3 years old). Interestingly, the pressure varies throughout the day as if something seals a bit better when the sun warms it up (sounds weird, I know). So in the mornings I often get barely any flow going whereas in the late morning or afternoon I get up to maybe 8 PSI (before this problem, I had usually around 15+).

So far I have tried all of the following:
- Cleaned skimmer and trap baskets
- Made sure no blockage is within reach (skimmer, etc.)
- Replaced Trap o-ring and intake flange o-ring on pump (I used o-ring sealer, too)
- Dis-assembled Jandy valve and re-applied o-ring sealer (o-rings look like new)
- Opened pump, checked for debris in impeller etc.. and checked o-rings (one small and one large in the Sta Rite). Looked good and re-assembled with o-ring sealer
- One after the other, taped pipe joints with heavy duty electrical tape to maybe identify any leak. I assumed that while this would not entirely fix it, it should at least show me a small variation in pressure.

So I am out of options that I can think of. It also puzzles me that the pressure changes for unknown reasons. The only next steps I see are:

- Take the pump out and bring it to a store that can check it, or
- Apply pressure to the system to find the air leak

Both seem to be a major pain in the neck so I am hoping to get some additional clues.

Thanks!

It sounds like you have a suction leak. Is there air in the pump basket when the pump is on?

Thanks for reading my post PoolDoc.

The flow into the pump basket is very limited. So it doesn't even fill up completely. Yesterday morning I had about 1-2 PSI, later in the day it built up to about 6-8 but the pump basket is still not entirely full.

Suction leaks are hard to find. Common locations include:

+ pump basket lid gasket
+ threaded connection to pump
+ unions
+ valve stems
+ cracks in piping
+ 'stuck' skimmer weir flaps (not a 'leak', but still brings air into piping.)