MAG 18 making buzzing sound

[Polkster13]

I think she may have been talking about the plumbing to the pump and not the pump itself. You can have a 2 inch inlet on the pump but if you put a 1.5 to 2 inch reducer on the intake, then the pump would not be getting the amount of water flow for which it had been designed.

[dow]

I think she may have been talking about the plumbing to the pump and not the pump itself.

Yep, that's what she was talking about. She also told me that if you're only talking less than 6" or so from the pump to the larger line, that it shouldn't have any impact, but if you're talking a longer run, then it could cause problems.

[Dozer]

Yep, you're having the same problem I did with a Mag on a closed loop. I never really could stop the chatter sufficiently so I sent it back and went with a good external magnetic driven pump. I found I could get a PanWorld for not much more than say a Mag18, and it seemed so much better for an external application. Also, I don't want to speak for anyone, but check with NaCl, I believe I read where he started with Mags and converted to PanWorlds for closed loops. Also, I have heard/read that Mags overrate their return flow rates, so don't necessarily be scared off when comparing an Iwaki or Panworld type pump that's rated only around 1000-1300gph to a Mag that's rated at 1800gph. In the actual application they may actually put out just as much or more. I'll let the physics/engineer types try to explain why- or the guys that have been doing this a long time. I was in your exact situation and someone on this board- I think it was Joshua- swore to me that a PanWorld rated at 1270gph would outperform an old Mag 18 I had- and he turned out to be right...

Btw, I'm thinking about selling the PanWorld I was just talking about to upgrade to a Tunze or Sequence pump. The PanWorld works great but I'm thinking I want more flow. Hope this doesn't sound like a sales job, honestly there are several people who I know would take it so I'm not trying to push it on you! But it is a great pump for a closed loop if you're interested let me know.

[NaCl_H2O]

... but check with NaCl, I believe I read where he started with Mags and converted to PanWorlds for closed loops.

Yup, I tried to use Mag5 & 7s for closed loops (don't compare to the MAG 12 or 18s. The small MAGs were cavetating badly and causing bubbles.

Al that aside, I use the MAG12s for other portions of my system and I am relatively happy with them, but will eventualy replace with PWs.

Panworld/Iwaki/Blueline are no doubt far superior pumps to MAGs. They do provide flow closer to their advertised specs, and from my experience, the MAGs produce far less flow than their specs given ANY head pressure.

[eric]

I think you have a cavitation issue, not in the pump but one of the PVC fixtures. Guess somewhere between the elbow and the inlet of the pump. Lower pressure or increased flow rate will cause a cavitation.

Any change if you close the inlet valve a little bit? Not too much.

I wonder...Something you could try, since your bulkhead is low enough to allow you to have a wide water level range. With just that loop running and both valves fully open see if the noise differs between a water level just above the bulkhead and the water level kept at the top of the tank. I'm not sure that raising the water level would increase the pressure or not. It's just something I would try if I were having the problem. Doesn't really provide any solution, but might show you're cavitating if the noise lowers if the water level is raised.

And then hmmm, I think someone suggested some eductors on the discharge of the manifold. Would that produce a similar back pressure like closing the valve?

[PsychFish13]

mousepads are awesome insulators for noise and vibration