Impeller Question

[Dabby]

I have a 1 1/2 HP Hayward Tristar pump that runs the waterfall and bubblers. We always had to cut the valves almost all the way off because the water flow was greater than we wanted - a gentle brook, not roaring rapids. A couple of years ago, I replaced the impeller with a 1/2 HP impeller. That caused a swing too far to the other side. The valves are all the way open and the flow is about where we want it, but the pump is extremely noisy. I want to replace the impeller again, but I'm not sure if I should go with a 3/4 or 1 HP impeller.

What would you all suggest?

Thanks.

 

[kadavis]

, this is another way if the feature pump is to big, plumb a bypass loop on from the discharge to the suction line

 

[mas985]

The valves are all the way open and the flow is about where we want it, but the pump is extremely noisy.

If the flow rate was about the same with the larger impeller, the noise should not be that much worse.

Are you sure you reassembled the pump correctly?

Does it sound like pebbles traveling through the pump?

If you close off the valve, does the sound decrease?

Can you post a video with sound?

 

[Dabby]

Let me back up:

With the original 1 1/2HP impeller and the valves wide open, the bubblers were more like fountains and the waterfall was roaring rapids. That's not what we wanted, so I would close the valves almost all the way off to get the desired effect. This would cause the water trying to pass through the smaller opening to be very loud.

I replaced the impeller with a 1/2HP impeller. Now with the valves wide open, there is too little flow and it sound like before, too much water trying to go through a little opening.

I would like be somewhere in between. I'm trying to get where I can leave the valves about half open and provide the flow we want and not try to force too much water through a too small opening.

I don't know if a 3/4HP impeller would still be too small or if a 1HP impeller would still be too large. Hopefully that makes since.

 

[mas985]

This may or may not help but here are the flow rates of the various TriStar pumps on plumbing curve C. This can give a relative feel for how flow rate changes with HP rating:

TriStar SP3205EE: 67 GPM
TriStar SP3207EE: 79 GPM
TriStar SP3210EE: 85 GPM
TriStar SP3215EE: 92 GPM

So going from 1.5 HP to 0.5 HP, you dropped about 30% in flow rate. If the 0.5 HP is not enough the next size up (3/4 HP) would increase flow rate by 18% which is more than half of what you lost with the first drop in HP (1.5 -> 0.5). A 1 HP impeller would only have dropped flow rate from a 1.5 HP by about 8%.

 

[Dabby]

That helps. Sounds like I would be better off going with the 3/4HP impeller. Thank you.