Q on old Jandy single speed pump

[JamesW]

Now I'm thinking I should open those valves because I could probably lower RPM even more and save more on energy costs?

Yes.

With the valves open and the old pump, the flow was probably between 110 and 120 GPM, which is about what I was estimating originally.

Open the valves and redo the readings (power, flow, pressure) at different speeds.

You should be able to lower the speed by a lot and the power usage should drop by a lot as well as the noise.

 

[jesse-99]

(Sorry I edited that post above because I was wrong --- I went back to open the vales and found they were already opened -- DOH, my bad).

The pressure side T's out of the 011056, into a 1.5" pipe (with valve to restrict for one beach jet/bubbler) and another 1.5" pipe (with valve to restrict one beach jet/bubbler). I can take a pic if you like.

 

[jesse-99]

Pic for reference

 

[JamesW]

If you have 2 separate 1.5" lines to the bubblers, that's OK since each line can do 51 gpm for a total of 102 gpm.

What size is the suction line?

What is the total length of the plumbing?

 

[jesse-99]

Suction side is 2". I'd estimate the total length of the plumbing to be approximately 130-140', but that's just me walking it off and a visual guess of where they ran the plumbing.

 

[JamesW]

2" PVC at 90 GPM is 8.8 feet per second and 12.4 feet of head loss per 100 feet.

Assuming 140 feet of pipe plus maybe 30 feet to account for 90 degree elbows, that is a total equivalent length of 170 feet and a total head loss of 21 feet for the suction.

You never want more than about 17 feet of head loss on the suction side as this can result in the pump cavitating.

The returns can be estimated at about 20 feet of head loss for a total suction and return head loss of about 41 feet.

The suction should have been at least 2.5" and preferably 3" due to the long runs.

The returns should have been 2 separate 2" PVC lines.

 

[JamesW]

Even when accounting for the undersized plumbing, the head loss still seems excessive.