Change impeller

[Steve21]

Hello all,

Just built my pool a few months ago (owner build). I have a dedicated pump for my water features (one bubbler, one 36”sheer descent, and two Pentair laminars). Each is controlled by its own valve and powered by a 2 H.P. Pentair whisperflow pump. The problem I’m having is, I believe the pump is too powerful. I have to throttle the valves down low, restricting output, for an acceptable flow. When I do this, the pump is very loud.

I think changing the impeller is a likely solution, but am unsure about what size to go with?

 

[cowboycasey]

Go to a 1.65 HP VS motor and get the perfect flow

Call inyo and ask for the correct motor but I think it is the square model... Also ask for the rebuild kit and get a Salt or SCS seal...

 

[mas985]

Yes, you can reduce the size of the impeller to reduce flow rate. But DO NOT reduce the size of the motor without reducing the size of the impeller. Reducing the motor size without changing the impeller will cause overload on the motor. However, you can reduce impeller size without changing the motor.

However, to get the correct size of the impeller, I need some additional information:

Current pump model#

Filter pressure with and without valve throttling

Filter gauge height relative to the water level

Suction side plumbing size and length to the pool. Single run or multiple suction runs.

BTW, you can "trim" the impeller if you feel like that is something you can do. I have done it before and it is really not all that hard to do. I can tell you how much to take off with the above information. Below is a picture of an impeller that has been trimmed to a smaller vane diameter.

 

[Steve21]

Current pump model#

Filter pressure with and without valve throttling

Filter gauge height relative to the water level

Suction side plumbing size and length to the pool. Single run or multiple suction runs.

Pump is a Pentair 011530. 3hp. 3.45 sfhp

Filter pressure with throttling 27psi. no throttling, everything open 15.

2 1/2” on suction side.

Length to pool, is about 45’

single run for suction, 4 separate runs to the water features.

 

[Steve21]

And filter gauge is about 40” above the water level.

 

[mas985]

The pump model you gave is different than the one in your signature. I just wanted to confirm. Does this pump have it's own filter?

Ok so here are estimates of operating points for the 3 HP pump:

Without throttling: 148 GPM @ 57' head
With throttling: 110 GPM @ 76' head

Now assuming different impellers/pumps and no throttling:

WF-4 (impeller # 073128) : 111 GPM @ 32.1' head
Note that you will need a new diffuser as well (072927)

The head loss is very low in the plumbing. Unfortunately, it isn't low enough for a waterfall pump.

BTW, if you want to trim the impeller, you can reduce the impeller vane diameter by 25% to get the same effect.

 

[Steve21]

The pump model you gave is different than the one in your signature. I just wanted to confirm. Does this pump have it's own filter?

Correct. I need to change my sig. and yes, the pump has its own dedicated filter, a Pentair 100sq ft clean and clear cartridge filter

 

[Steve21]

The pump model you gave is different than the one in your signature. I just wanted to confirm. Does this pump have it's own filter?

Ok so here are estimates of operating points for the 3 HP pump:

Without throttling: 148 GPM @ 57' head
With throttling: 110 GPM @ 76' head

Now assuming different impellers/pumps and no throttling:

WF-4 (impeller # 073128) : 111 GPM @ 32.1' head
Note that you will need a new diffuser as well (072927)

The head loss is very low in the plumbing. Unfortunately, it isn't low enough for a waterfall pump.

BTW, if you want to trim the impeller, you can reduce the impeller vane diameter by 25% to get the same effect.

How many horsepower with the above setup put me at?

 

[mas985]

The WF-4 is a full rated 1 HP pump (1.65 THP). But there really is only a very loose relationship between HP and flow rates. It is really the head curve that is important.

 

[Steve21]

The WF-4 is a full rated 1 HP pump (1.65 THP). But there really is only a very loose relationship between HP and flow rates. It is really the head curve that is important.

Thank you so much for your help. I really appreciate it