Pump LOUDER when all returns open

[Dlittle6]

Hello, i just noticed this when i closed a return to vacuum the pool. The pump got significantly quieter with only 1 return line open. Both returns are same length and are aqua genie skimmers.

Any idea why it would be so much more quiet? I can get video of sound if needed.

 

[ajw22]

Welcome to TFP.

What model pump are we discussing?

Why is getting quieter a problem?

 

[Dlittle6]

Welcome to TFP.

What model pump are we discussing?

Why is getting quieter a problem?

Thanks!

It’s a Black and decker 1.5hp variable speed. The quieter I don’t believe is the problem. I believe it getting louder is a problem. Maybe not tho.

 

[sktn77a]

It could be cavitating with too little return resistance. Does it sound like it has small rocks rattling around in it?

 

[ajw22]

Thanks!

It’s a Black and decker 1.5hp variable speed. The quieter I don’t believe is the problem. I believe it getting louder is a problem. Maybe not tho.

What RPM is it running at?

How does your filter PSI change when you close one return?

 

[Dlittle6]

What RPM is it running at?

How does your filter PSI change when you close one return?

With return fully open, (pump is noisy) psi is 4 at 3,000rpm. With 1 return closed, psi is at 10 at 3,000rpm and much quieter.

At 2300rpm psi is virtually zero with all returns open, with 1 return closed psi is 6 and much quieter.

 

[Dlittle6]

It could be cavitating with too little return resistance. Does it sound like it has small rocks rattling around in it?

This could be it. I didn’t know return resistance is a thing. But yea that’s kind of the sound. Also like rapids of water.

 

[Lake Placid]

With return fully open, (pump is noisy) psi is 4 at 3,000rpm. With 1 return closed, psi is at 10 at 3,000rpm and much quieter.

At 2300rpm psi is virtually zero with all returns open, with 1 return closed psi is 6 and much quieter.

Just to be clear….returns are the lines that supply water back to the pool….the jets/eyeballs in the wall and their lines as it were. They are the pressure side of the system. The water outlets are where the water leaves the pool to move back to the pump and could be skimmers (the aqua genie you reference), main drains, vacuum outlets etc and are the suction side of the system. It’s not unusual to see an increase in psi when you choke down a skimmer. The noise you’re hearing certainly could be cavitation. When both skimmers are open do you see any air, bubbles, lower water level or increased turbulence in the pump?

 

[Dlittle6]

Just to be clear….returns are the lines that supply water back to the pool….the jets/eyeballs in the wall and their lines as it were. They are the pressure side of the system. The water outlets are where the water leaves the pool to move back to the pump and could be skimmers (the aqua genie you reference), main drains, vacuum outlets etc and are the suction side of the system. It’s not unusual to see an increase in psi when you choke down a skimmer. The noise you’re hearing certainly could be cavitation. When both skimmers are open do you see any air, bubbles, lower water level or increased turbulence in the pump?

Yes returns supply water back to the pool.

When both returns on the aqua genie are open, the cartridge filter does get air in it. I thought it was an air leak for the longest time and could not find it, also the returns would shoot out small tiny bubbles.

Now with the 1 return closed, I get zero air in the cartridge filter and zero bubbles into the return.

I have 2in suction and return plumbing. Half of it is accessible. And The rest is under ground.

 

[Lake Placid]

I’d postulate the returns on the A.G. are introducing enough air and or turbulence which is getting sucked right back into the skimmer such that with both open the pump cannot overcome it and is cavitating. When you close 1 the pump ceases to cavitate because it can draw a full less turbulent column of water.