Pentair SuperFlo VS spa stops overflowing after a couple hours, air in the pump basket

I’m experimenting with a new Pentair SuperFlo VS speed pump. I’ve tried running it at low RPMs (700-1,000 at 50 RPM increments) and every time I get the same result. For the first few hours water will spill over the spa and into the pool. However, after a few hours the spa stops overflowing and this correlates with air showing up in the pump basket. If I run the pump at full speed the air quickly flushes out and I can dial it back to a low RPM and water flows over the spa again.

Any idea what is causing this?

Also a couple bonus questions:

  1. The previous owner has connected the PVC pipe leading to the filter and the PVC pipe leaving the filter with a rubber tube. They’ve got cheap plastic (compression?) nuts that are presumably meant to secure the rubber tubing and one of them has broken. What is this for and what is it called so I can look into repairing it? Anybody know where I can find a cap that can screw on to the male threading that the (compression?) nuts currently screw onto?

  2. I’d love to run the pump at a low speed all day and schedule short bursts of high RPMs to flush out the air and get water flowing over the spa again, but it seems the schedule is fixed to 24 hours and there are only 2 speed changes allowed during that time (1 → 2 and 2 → 3). That limits me to shcheduling one higher PRM time per day. Is there any way around this?

sounds like you have a spa suction valve open or the spa return valve not cracked and the air could be coming from The lid or possibly one of those valves. Also if you have High pressure on your filter they may need to be cleaned and or back washed depending what kind of filter you have. But yeah I would change that’s fitting on the pump mainly the suction side or if water is low and it’s sucking water from the skimmers could be an isue.

Is there water leaking out on the ground or do you hear air leaking at anywhere by the pipes or valves or lid. When you buy it off