[Pinski]

So I picked up March pump to help with my all-grain transfers.  I've heard (and would like to verify) that a ball valve isolation/restriction should only be installed downstream of the pump outport.  My real question is about operating the pump and restricting the flow.  Are there any rules of thumb about this?  I'm concerned about restricting the flow too much and damaging the pump.  Or running the pump too long.  Any tips are greatly appreciated.

[Brewdogz]

you are correct, put a valve on the pump outlet for restricting flow.

I assume this is a magnetic drive pump.  The pump doesn't really care how much you restrict the flow.  As long as there is liquid in it you should be fine.

[denny]

Once I get the pump primed, I'll often just shut the valve on the output and let the pump keep running.  No harm done.

[mabrungard]

Yes as long as the pump volute is full of liquid, you can close the valve on the outlet side of the pump to zero opening without any damage.  The load on the motor will actually decrease as the valve is closed and the flow decreases.  You will be able to hear the motor speed up as you close the valve and the motor load decreases.

I have found that its a good idea to keep the motor running throughout the time that I'm recirculating my wort with my March pump since the impellor can seize to the shaft due to sugar buildup.  I just close the output valve as needed and the impellor never has the chance to seize.  Once I've performed the wort runoff and sparge, then the concentration of sugar in the pumped wort goes down and the chance of seizure goes away too.

[Pinski]

Can you attach a ball valve directly to the outlet port threads or should it be a minimum distance from the valve?

[narvin]

Can you attach a ball valve directly to the outlet port threads or should it be a minimum distance from the valve?

Yep.