Refitting antique piston pump for direct PV

I have acquired an elderly piston pump. A Fairbanks Norse model 41, seems in pretty good shape, guessing the seals will need replacing.

I am planning to use it to pump water from a remote secondary reservoir to the central reservoir, after swapping the motor for a DC unit suitable for direct drive from solar panels.


The motor on it now appears original, marked Fairbanks Norse, 1/4HP, 5.2A/120V, 1725RPM. I have read that these pumps originally came with a 1/6HP motor and switched only due to the more common 1/4HP being cheaper, so it seems I should have some wiggle room downwards.

It seems reasonable that a somewhat slower stroke rate, due to altered motor RPM and/or altered pulley sizes, would be fine, simply reducing flow. It seems like the motor could be derated if the pump was doing less work, but there is probably a minimum..

I would assume that a substantial increase in pump rate would be a poor decision.


Looking for any input on speccing the motor, it will be running direct off 300W solar panels, thinking that 3 may suffice but obviously depends on the motor.

It needs to pump about 500ft with perhaps 30ft of total rise, half of it suction when the lower reservoir is nearly dry.


I also need to decide on the size of the line. I will see about getting the pump running on AC, and determine a rough flow rate, to inform this decision.. but input is again welcome.

Your pump will draw about 600W. If you want to run it on solar, have you considered a battery and an inverter so you don't have to replace the motor? A charge controller can be sourced for about €20, for batteries even an older car battery is probably suitable for your goal.

I have done the old truck battery thing, and the cheap deep cycle thing. Hate it. Also the cheap charge controller thing... I have various portable pumps, fencers, and tools running off this sort of system all over the damn place, and something is always failing at an annoying time.

I would much rather jump hoops now, as I expect a direct PV setup to be extremely reliable once all is done right!