What is the best way to increase head?

[wpbucher]

I've had the weirdest issues with my pool build.

The pool has a waterfall. Based on a waterfall at a house we rented, I figured I needed 80-100 gpm to make it look nice.

When I developed the specification, I had a 2" pipe to and from the waterfall and a 2-way valve to adjust flow.

Waterfall is about 40 feet from equipment pad and about 6 feet of rise above it. Probably, 5-7 90 degree elbows between pump and waterfall.

I allowed the pool builder to pick the pump.

The PB decided on his own to make the piping 3"....and he wanted to use a 2 HP WhisperFloFX.
I told him I didn't need/want that much flow.
So I agreed to a 2HP WhisperFlo WF-8.
I figured I would use the 2-way valve to restrict as necessary.
We don't run the waterfall all the time...so no big deal as far as energy consumption, etc.

The very first time the pump was turned on it made a screaching sound.

PB contacted Pentair rep and this was the response:
Sounds like it is what we call "freewheeling" or at the far end of the pump curve.

Pentair suggested restricting the flow with the 2-way valve. I tried that and the pump became quite.
The valve is a FullFloFX valve. If 9 o'clock is open....I have to turn the valve to about 10:30 or 10:45 before the pump gets quite.

The problem is that the valve makes about as much noise as the pump when I restrict the flow.
Once I get to 11 o'clock all is quite, but the flow at the waterfall is not enough.

PB also suggested piling rocks on top of 3" opening in waterfall basin to help restrict flow. I tried that...helps a little. If I seal up the pipe to much....Old Faithful for a while....until the rocks are moved by the water pressure. I'm talking 20 pound rocks!!!

I first thought...get a smaller pump.
When I look at the pump curves, all the pumps "max out" above 20 feet of head.
I'm not sure that I've got 20 feet of head since the PB used 3" pipe.
Thus, I'm afraid a smaller pump will simply pump less but be just as noisy because it is at the far end of its pump curve.

FINALLY MY QUESTION:

How can I quietly introduce a sufficient amount of head so that my waterfall pump is not at the far end of the pump curve?

I've read a lot of posts trying to reduce head....this might be the first one trying to increase head.

Thanks for your help TFP!!!

 

[jblizzle]

Add a valve in the line and partially close it.

Admittedly, I only read the last part of your post.

Edit: and now I see my post was not very helpful

 

[mas985]

A throttling valve is probably the easiest way to reduce flow rate but as you found out, it also makes noise. Anything that increases head in a small amount of area, will be louder than if you increased head by a long section of smaller pipe (also an option). However, you can put the valve near the water fall too so it is masked by the sound of the waterfall. You might think about downsizing the impeller so you don't need to restrict the flow as much plus pump noise will be less too.

What type of valve are you currently using? The Jandy neverlube might be quieter than a standard ball valve.

Just to add to this, the PB really should have used a waterfall pump which is made for high flow rates and low head loss.

 

[JasonLion]

Others are faster at answering then me. I am repeating a little, but there is some new material here

You can easily convert your existing pump to a smaller pump simply by replacing the impeller. Using a smaller impeller will help the underlying problem a little, though not completely. You will still need to keep the valve partially closed. The big advantage of using a smaller impeller is that it should reduce the noise significantly.

Another approach is to spread the flow restriction out across several valves/pipe restrictions. That will reduce the noise level. There are a number of different ways this might be done. One of the simpler ones would be to add a new segment of pipe of a smaller diameter that "wanders off" somewhere and then comes back to rejoin the existing pipe. The longer path and smaller pipe will add some dynamic head.

 

[wpbucher]

Thanks for the responses.

I think the basic problem is that the PB didn't use a waterfall pump for my waterfall.

My waterfall is the classic high flow low pressure application......it is "made" for a waterfall pump.

Only PB (former PB) knows why he did not install a waterfall pump for the waterfall.

Thanks TFP!!!

 

[Isaac-1]

You could always add an additional filter to the line that should create a fair amount of back pressure.