Simple question on a fairly simple system.
We bought a foreclosure six years ago and have rehabbed the pool from green pudding swamp to crystal clear without having to do anything with the old pump. I added an Aqua Rite Goldline SWG as soon as we drained the pool and we had it resurfaced two years ago.
Yesterday, I replaced my old 1hp coffee grinder (that's what it sounded like at the end) with an Intelliflo VS+VSRS (011017) and upgraded from a Hayward C900 to a C1200 filter. I was able to take out a bunch of unused PVC from where the previous owner must have removed/bypassed a heater and took out about 360° of turns to improve the flow a bit. The system tested out beautifully with no leaks and great flow. However, when I ramp it down to the lower rpms, below 1500rpm or so, the entire pump vibrates and shudders. As soon as I bump it up above 1500rpm it smooths right out.
I have 2" PVC from the 3-way Jandy valve to the pump and the main drain is 2". The skimmer and vacuum (1 1/2") are on a separate 3-way Jandy valve the feeds to the other side of the main drain valve.
Pump output to filter is 1 1/2" and return line from filter to pool is 1 1/2". (I could have done 2" pump to filter, but still would have the 1 1/2" return line to the pool.)
Any clues as to why it would vibrate at the lower speeds? Would increasing the pump-to-filter to 2" help? I'd still have the downsizing coming out of the filter, but perhaps that would be better? (Yes, I've searched the forum to no avail.)
As I said, it's a fairly simple system setup with no automation. After some reading here on TFP, I rewired the new pump to the hot wires coming into my timer so I could use the built-in timer function. It's not ideal, but I'm going to keep the salt cell on the old pool timer until I can find time to either add a control panel or build the relay/timer rig I've seen on TFP.
Pentair Intelliflo VS+VSRS
Aqua Rite SWG
Three eyeball returns
One mystery return - probably old air jet
Skimmer and Vacuum 1 1/2"
Hayward C1200 filter
No spa, waterfall, water features, etc.