Noise from Iwaki MD70 (not fan noise)

[GoldStripe]

I've started plumbing my new tank out in the garage last night. got the drains done, got the return line in temporarily. When I hooked the pump up it was unusally noisy at the volute. Sounds like air being spun around the impeller area. So, today I hooked the pump up to my Brute trash can for a test. This time with hard PVC the whole way. Same noise!!

I just discovered that if I put my hand over the output of the pump (creating head pressure I guess), the pump shuts right up. Any idea why or how this is happening? I assumed the pump would get noisier with more pressure. Anyone have experience with this pump?

 

[floridareefs]

No exp, but try to take the impellor part out and put it back in. I think your assessment of trapped air in that chamber is spot on.

 

[GoldStripe]

I took the impellar apart last night but it didn't seem to have an effect. Today I tried loosening and tightening the bolts that hold the volute to the pump body and that didn't change anything.

 

[GoldStripe]

I just switched the out line to 3/4" and the pump with silent. I wonder if I could bump up the intake to 1 1/4" and leave the output at 1" would have the same effect?

 

[GoldStripe]

Rob, you've been around Iwakis before I'm sure. Want to chime in?

 

[robwsup]

Are you using it for closed loop or return?

You may notice that it quiets down a bunch as it pumps against some head loss. Try pumping 4' up.

You are on the right track with a larger intake than exhaust. Try 1.5" in and 1" out.

 

[GoldStripe]

Hey Rob, do you happen to have any eductors around the shop? I started a new thread for this.

 

[GoldStripe]

Noise is getting better. I replaced the intake side with a slip bulkhead, and then a 45. From the 45 goes the spaflex around to the slip x fpt on the pump. The noise is still there but much improved. Next I'm going to tee off up top using 3/4" for the 2 returns. Should be enough head pressure without choking the pump too much. Oh and I'll also put a ball valve on the outlet which will slow down the flow if I need to. Thanks for everyone's help