Sizing a new pump

[mas985]

Looks like these two pumps pull the same amps. The WFDS-4 is one HP and the WFDS-26 is 1.5 HP. The -4 costs about $75 more than the -26. Does it make sense they both have the same amp rating? Wouldn't make more sense to go with the 1.5 in my case then for the higher lift?

The WFDS-26 is an up rated pump while the WFDS-4 a full rated pump but other than the label, they are identical in performance. So it doesn't matter which you get. One of the problems with pump ratings is that it causes confusion.

Will these pumps move water on slow speed in my application? I am figuring 50 Ft of head, looks like slow speed graph tops out at 22 lbs.

Yes, they will still move the water on low speed. But head loss is dependent on flow rate so on low speed, head loss is about 1/4th that of high speed. If you indeed have 50' of head on high speed, on low speed you would have 12.5' of head. But you don't need to figure head loss to know that low speed is always around 1/2 the flow rate of high speed.

But because of the lift, you will need to always prime on full speed and then switch to low speed. The pump should not lose prime when shut off but if does, it will need to be started on high speed. If you get a two speed timer, that should solve any priming issues because you can always start the pump on high speed and then switch to low speed.

[lstinthot]

I installed the WFDS-26 today. Went pretty good. Took a little longer than expected to complete. The discharge pressure on high is 16# and maybe 2# on slow speed. Not sure what others are seeing for slow speed discharge pressure. I did change the piping on the return of the filter. It now comes out of the filter and goes back to the pool without going through the heater or clear water metal copper system. Very little water comes out of the vent when I open the vent on top of the filter in slow speed. I am returning to the bottom drain of the pool. We keep this lineup during the spring to help heat the pool. Have not tried going back to the return jets.
Pump is significantly quieter then the ultraflow 2HP even on high speed.

New filter elements will be in Friday.

[mas985]

Low speed will have lower pressure and theoretically should be about 3 PSI but gauges get inaccurate at low PSI. 1/2 the flow rate results 1/4 the head loss in the plumbing.

But is the pump basket staying full between pump runs?

[lstinthot]

The pump started up immediately the following day. Pump was full pressure came right up to 16# . Best it has ever done. I'm thinking slow speed could have started moving water from the start.

[mas985]

As long as the the pump doesn't lose prime after being off, you can start it on low speed if you want.

[lstinthot]

I plan on starting the pump in slow speed tomorrow to see how it does. We will add timer dogs once we are happy with the pump starting with no issues.