Knocking/Hammer/Thumping noise from pipes when pool pump shuts off

[JamesW]

Can you report the readings for Flow, Pressure, RPM and Watts at the different speeds?

 

[Cartman269]

Can you report the readings for Flow, Pressure, RPM and Watts at the different speeds?

Unfortunately the pump is an IntelliPro 2 VST and does not show flow on the display. I have a chart in the manual for flow but it shows the graph in total head feet for flow, not sure what that measurement would be, however for the pool alone (without solar), it is an in-ground 6' on the deep end approximately 40 feet from the pump equipment. With solar on, the solar panels are 20' above the pool equipment at the highest point and 12' at the lowest as the solar pvc pipes run along the roof. The panels are approximately 85 liner feet from the pool equipment with a total of 7, 90 degree bends in both the supply and return piping. Not sure if that's too much information, but better to have it and not need it than the other way around, lol. I have attached a copy of the flow chart.

The readings I can give you are as follows
Solar Panels On
Pressure - 18 psi
RPM - 2,450
Watts - 934

Solar Panels Off
Pressure - 8 psi
RPM - 1,700
Watts - 319

 

[Cartman269]

A calculator is not necessary. There is no turnover requirement for a residential pool. There are only a couple of factors to consider depending on how you run your pool and the equipment you have.

1) SWG - RPM needs to be high enough to trip the flow switch. But that is usually pretty low RPM for most setups. I would try 1000 RPM and see if the SWG still works.

2) Skimming - Find the lowest RPM where water travels over the weir door instead of around the sides. This will have a higher surface velocity so that skimming is more effective.

3) Heating - For you this is probably not a factor at all since you have solar but some heaters require a certain flow rate or pressure to operate properly.

The idea here is run at as low an RPM as possible to keep energy use as low as possible. I suspect you can operate well below the current 1750 RPM without any impact.

I have dropped my pump down to 1,000 rpm when solar is not in use. The flow light on the SWG is still lit and the weir is still open with water flowing over it. The pump is now using 70 watts instead of the 300+ watts it was using at 1,700 rpm. I am hesitant to go much lower, as I can’t see saving much more power and things seem to be working ok. Thanks for the tip, my electric bill will certainly be better!

 

[mas985]

For most VS pumps, there is very little benefit going much lower than around 1000 RPM due to a constant drive electronics power.

An added benefit, is that you will probably not hear the thumping anymore with or without a new check valve.