Another pressure question

[Sumo1]

I've had earlier questions about operating pressures before (see "Pressure problem"). Now I've noticed when I turned off my skimmer to wait for the big oak tree to finish dropping leaves, the filter pressure dropped 5psi and stayed down. I would think that drawing water from more sources than just the main drain would have lowered FP.? TIA

[JohnT]

I would think that drawing water from more sources than just the main drain would have lowered FP.? TIA

When you close the skimmer, you are restricting the amount of water the pump can take in, so you are limiting how much it can pump. Pressure is measured on the outlet side of the pump, and is an indication of how hard the pump is working to force water through the filter and return plumbing. The less water the pump is trying to push, the easier it is to get that water through the system, so the pressure will be lower.