I'm looking at setting up a basic RIMs system. I just bought a march pump with the 1/2" NPT males on each end.
I was thinking i would set the pump up with the inlet up and the outlet facing down. However, i see a lot of people setting up the pump with outlet up. Wouldnt this cause priming issues????? With the inlet up and the outlet down you should be ale to natureally fill the pump head via gravity and not get much air trapped.
You have to consider the internal shape of the pump head. The inlet goes to somewhere in the center, the outlet comes from the outer edge. If the outlet is down, you'll wind up with a big air pocket.
Just like bleeding brakes on a car, you want your outlet at the highest point so air bubbles will rise out of it, otherwise you're just fighting gravity.
I have my pump mounted vertically with the pump head down. The inlet and outlet are essentially on the same horizontal plane. I use a small bleeder valve on the output side between the flow control valve and the pump. No priming problems at all. None. I'm running a direct fired RIMS with this pump. The bleed valve is also handy for grabbing wort samples on the fly during the sparge. I pump from the MT to the BK during the sparge, so without the bleed valve, it's a hassle to grab a sample of the runoff and this is something I need to do multiple times during the last part of the sparge. The Little Giant pump has been performing flawlessly going on about five years now. It's only a little pump, but it's a Giant!
We mounted ours with the inlet up first and found the exact issues stated above - the bubbles wouldn't rise out of it - so we flipped the pump before brewing this weekend and it worked out best to have the outlet facing up.
March pump set up
Linear Mode
