It has been almost a month and I wanted to report on my findings. My original question was why did this happen when I got a new variable speed pump. I am 100% sure why now, it is the pump running at slow speeds and gravity (someone can probably explain this better). My equipment is a little wacky, out from the pool pump there are 3 pipes that go down to the jets in the pool. Also water flows through my spa pump and into the spa which has to go up above the ground. The spa spills over in the pool.
From a PSI perspective, running at 2500 rpms is at 12-13 psi and it's been there since the last backwash over a month ago. Nice! Below is a list of various findings I have came up with from a month of testing.
Scenario 1:
Run pump at 3450 for 5 minutes, then reduce to 2500rpm. To keep the math easy, guess that 50% of the water flow is coming down the spillover and 50% of it is coming out the jets in the pool. The slower moving water wants to take the easiest path, down instead of up into the spa. Over the course of 12 hours the water flow at the spillover is now 40% and the water coming out of the jets is 60%. Over 24 hours the spillover is now at 20% and the pool jets are at 80%. Slowly the water is taking the easier path. Turn the pump off for one second, 3450 for 5 minutes then 2500 and you are back to 50/50.
Scenario 2: The pool cleaner
While running the pump at 2500 rpm with 50% spillover and 50% jets, run the pool cleaner for an hour. The pool cleaner has a booster pump. While the pool cleaner is running the flow at the spillover is greatly reduced, say down to 20%. Now turn the robot off and the spillover will not go back to 50%, I think it's easier for the water to go downhill. So now maybe it's 30% at the spillover and 70% at the pool jets. An alternative that works fine is to run the pump at 3100rpm or 3450rpm while the cleaner is running, then switch back to a lower speed after.
Scenario 3: Children in the spa
Running the pump at 2500 rpm, with 50/50 split of water flow, the kids get in the spa and splash around. The splashing around in the spa is disrupting the flow of water. They play in and out of the spa for hours and now the flow at spillover is 30% and the pool jets are at 70%. I found it interesting that them being in there could affect the flow.
Scenario 4: Slower speed to faster speed
Running the pump at 1750 rpm and the spillover is barely going, 5% at the spillover, 95% at the pool jets. Now increase the speed to 2500. The spillover is going to increase a little but not to 50/50.
For the past couple weeks I've been running 3450 for 30 minutes and then 2500 for 14 hours. Leave the pump off overnight. Is there any advantage to running the pump at a super slow speed, like 1400 rpm, overnight vs leaving it off?