Can pumps introduce oxygen?

[Grannyknot]

Quick question....
I've been trying to track down sources of hot side aeration. I used to think hot side aeration was a myth, and did nothing to the beer, but in the past year I've introduced a few new processes to my system, some which could lead to aeration of the wort, and I've noticed a significant decline in my hop aroma & taste.

So can my steelhead pump introduce oxygen to hot wort?

I only ask, because when it is coming out the other side, it looks like water that comes through an aerator screen in a kitchen faucet. I guess maybe bubbly is a terrible enough way to describe it?

Please don't turn this into a hot side aeration debate. Only asking about aeration from a pump. Thanks.

 

[dyqik]

Any kind of leak on the inlet side could pull air into the system if the pressure is below atmospheric. This might not show up as a liquid leak with the pull off, as the pressure difference is in the opposite direction then. The pump head itself could have a leak as well.

I assume that the wort being returned isn't allowed to splash, and that the inlet is fully submerged.

But if you are pumping liquid very close to boiling, then cavitation can occur, which would look like air bubbles, but without the consequences.

 

[Grannyknot]

Thanks for the response.
I bet what I'm seeing is cavitation.

 

[wardens355]

If you choke the flow down with a discharge-side valve, you can reduce cavitation and entrainment of bubbles. I recirculate during the boil to disinfect the pump and tubing prior to whirlpooling and usually choke way down to get low flow, which reduces the probability of the pump binding/stalling. Once you start cooling, you should no longer have cavitation and entrainment of bubbles, assuming your suction tubing and connections are set up properly. Is this issue only with boiling wort?

Edit: If your pump discharge is splashing or cascading, you will get some dissolved oxygen in there. I recirculate from a submerged inlet to a submerged outlet, so no splashing.

 

[whovous]

The other thing to look for is noise. Your pump should hum a little, but otherwise be completely quiet. If you hear a slight hissing or bubbling sound, then you are listening to air being pulled through your system along with the wort. Check all connections, or just try pushing each one tighter, one at a time. If pushing makes it quieter, you've found your problem.