Pump flow control question

[brewbrew]

I'm just putting together a HERMS recirculating mash system - my first use of pumps in brewing. The pump I'm using is the Malt Miller £85 mag coupled one.

If I need to restrict the flow (which I think is unlikely - but I want to be ready in case I do), am I correct to think that the restriction tap can only be on the outlet side of the pump? Or can I restrict the inlet (eg the outlet ball valve on the recirculating hot water source)?

I have found lots of positive advice that these types of pumps can be restricted without damage - but in my mind, if I restrict the inlet side, I wonder if it will end up "sucking dry"?

Thanks for any advice you might have.

BB

[guypettigrew]

Best to restrict on the outlet side of the pump.

Guy

[Kev888]

Yes, as Guy says - it is okay to restrict the outlet side to slow the flow.

With this style of pump the inlet should be as open and free flowing as possible, plus the pump should be well below the liquid level in order to create a positive head. Both of these things help to keep reasonable flow to the impeller and pressure around it - if this doesn't happen performance will suffer and it may get cavitation or even a semi-dry impeller, which can damage the bearings.

[mark1964]

Restrict on the outflow with either a ball valve tap or washing machine on off tap. I used the latter. If your using a mag pump it won't harm it