Interesting pump issue


Well-known member
May 12, 2018
Adelaide (Australia)
So pretty standard solar setup with solar Matt on second story roof , vacuum release valve on roof and pump at ground level all on its own system seperate to main pump and filter.

has worked fine for the year I’ve had the house and pump has been there for at least 6 years.

Pump recenlty died

replaced pump then came home one day and impeller on new (Davey silensor sls 200) had snapped off clean and failed ( motor was still spinning )

Replaced impeller and went again. This time noticed when solar turns itself on it gets going nice and smooth

but when pump switched off ( if solar says so ) then switches back on again shortly , it sounds like the pump is fighting something (it’s really weird) it sounds like it’s spinnibg but doesn’t pull water through suction or push out of pool jet but basket is full . It’s almost like some sort of hydraulic lock ?

i have noted there is no check valve and when switched off water drains back to pool from roof and from upstream of outlet back to pool through the pump (can hear it spinning)

does this sound like a check valve at the pump outlet will allow it to switch on and off easier ?

inam now just running pumpnon timer during day so it switches on in morning and off at end of day and there are no issues .

only the issue of turning it off then back on again quickly



TFP Expert
Mar 2, 2011
It's probably spinning the impeller backwards as the solar drains. If the impeller gets partly unscrewed from the motor shaft and then the motor turns back on, the shaft will begin spinning into the threads in the impeller and create a big impact when the threads get tight. That can cause the impeller to shear off.

There should be a check valve to prevent water from coming back toward the pump.

If the impeller is spinning backwards when the motor turns on, it might even cause the motor to run backward.


TFP Expert
Mar 2, 2011
Typically, the check valve goes on the outlet of the filter, but you can put it at the outlet of the pump.