Estimating filter pressure for a new pump?

[gordiec]

I’m seriously considering replacing my one year old 1.5 hp Hayward Super Pump with a Pentair Whisperflo 1 hp uprated, two speed pump (WFDS-24). The thought of a lower electric bill appeals to me, but I really like the idea of a quieter, more efficient pump.

I've read the excellent "Hydraulics 101" thread several times, but still haven't figured out how to estimate the operating filter pressures with the new pump. My current filter is a Hayward S244T sand filter and it runs at 13.5 to 14 psi when clean. Any idea on how I would I go about estimating them for both low and high speed?

Thanks,
Gordon

 

[mas985]

The WFDS-24 is actually a more powerful pump than the 1.5 HP Super Pump (SP2610X15) so your pressure should actually go up. However, the Whisperflo is about 6% more efficient on high speed so it can produce higher flow rates using less energy than the Superpump. The Superpump is a lower head pump so tends be on the low side with flow rates and pressure. I don't know your exact setup but making some guesses to get the pressure right:

SP2610X15: 66 GPM, 38' of head, 13 PSI, 2.65 Gallons/watt-hr

WFDS-24 (high): 75 GPM, 50' of head, 17 PSI, 2.84 Gallons/watt-hr
WFDS-24 (low): 37 GPM, 13' of head, 4 PSI, 6.05 Gallons/watt-hr

The Super Pump comes in a two speed version so you could just replace the motor to get a two speed if you want to save some money and not have to redo the plumbing.

 

[gordiec]

Mark, thanks so much for your reply.

I had thought about replacing the motor on the Super Pump, but see now that I had over-guesstimated the pump head (my tubing is all 1.5" and I was thinking it was closer to 60') and as a result thought the pump was moving a lot less water than it does. Perhaps swapping the motor would make more sense -- I'll have to crunch some numbers and think about it.

Thanks again!
Gordon

 

[mas985]

I guessed at what you had for plumbing but now that I know it is 1.5", I can make a better guess. Also, about how long are your runs from the pool to the pump? Do you have a single suction line or more than one?

Assuming a single suction and 40' runs:

SP2610X15: 51 GPM, 50' of head, 13 PSI, 2.25 Gallons/watt-hr

WFDS-24 (high): 58 GPM, 64' of head, 17 PSI, 2.3 Gallons/watt-hr
WFDS-24 (low): 28 GPM, 17' of head, 3.4 PSI, 4.9 Gallons/watt-hr

1.5" piping makes this a little worse.

 

[gordiec]

Thanks for your time on this Mark.

The pad sits 5' above the pool (FWIW the Super Pump has had no problem establishing a prime at this elevation).

A single suction line has a tee at the pump and draws from two skimmers.
Skimmer 1 has approximately 45' of tubing, skimmer 2 about 65'.

After the filter and just past the SWG cell, the high pressure line tees. The first side of the tee feeds the bubblers on the stairs and the second side tees again to feed two returns to the pool. The bubbler line has about a 30' tubing run, return 1 has 60' and return 2 has 45'. All these measurements include the vertical tubing runs (~9' for each).

 

[stev32k]

Interesting - I have the same pump and filter as you, 1-/12 H.P., Hayward 244T sand filter and my discharge pressure is always 24 psi when the filter is clean. I guess the pressure difference is a function of the downstream piping configuration.

 

[mas985]

The difference in pressure can also be due to the suction side. Higher head loss on the suction side will reduce filter pressure but I suspect in this case, the lower head loss is due to the return side.

This is probably about as close as were going to get to what you might actually have.

SP2610X15: 55 GPM, 48' of head, 13.6 PSI, 2.4 Gallons/watt-hr

WFDS-24 (high): 61 GPM, 61' of head, 18 PSI, 2.5 Gallons/watt-hr
WFDS-24 (low): 30 GPM, 16' of head, 2.1 PSI, 5.2 Gallons/watt-hr

Overall efficiency on high speed will probably not be that much different between the two pumps.

 

[gordiec]

Mark, thanks again -- I'll make a note of those numbers and will let you know what the filter reads if I change out the pump (I'm still looking into just changing the motor out for a two speed motor).

stev32k - does your filter making any popping sounds when the pump is running? Mine does, but I've noticed it seems to quiet down when the pressure goes over 15 psi. One of these days I'm going to open it up and take a look inside, but it seems to keep the pool clean so I'm going to leave it alone for now.

 

[brucemoose2]

stev32k - does your filter making any popping sounds when the pump is running? Mine does, but I've noticed it seems to quiet down when the pressure goes over 15 psi. One of these days I'm going to open it up and take a look inside, but it seems to keep the pool clean so I'm going to leave it alone for now.

That's probably air making its way out of the lines as your pressure builds when you first turn on the pump. If you didn't have the pump basket open, you may have a small leak in the gasket.

 

[gordiec]

Thanks for that, but I don't think that is what is happening with my filter. It makes the popping sound for hours on end until the filter gets dirty enough to get the pressure over 15 psi (weeks after back washing...). My system seems to be air tight as there is no air in the pump basket, even if the pump is left off overnight.

There was another poster who reported the same thing and I was wondering what others saw / heard with similar filters.

 

[brucemoose2]

Thanks for that, but I don't think that is what is happening with my filter. It makes the popping sound for hours on end until the filter gets dirty enough to get the pressure over 15 psi (weeks after back washing...). My system seems to be air tight as there is no air in the pump basket, even if the pump is left off overnight.

There was another poster who reported the same thing and I was wondering what others saw / heard with similar filters.

I have a Hayward S310T2 which is just a larger version of your filter. My filter very briefly makes popping/crackling sounds right after I've introduced any air into the system - through the pump basket or while hooking up the vacuum, for example. My clean pressure is between 14 and 15 PSI so I don't know what would happen if I tried running through the filter at a lower pressure.

 

[gordiec]

Thanks for the feedback.

My pool builder was originally going to put in a 1 hp pump but decided to go with 1.5 because he felt it would do better with the 5' lift from the pool to the equipment pad. I hadn't found this site yet and didn't know any better at the time. The 1 hp pump might be a better fit for the filter and the pool and is one of the reasons that I am now looking at the two-speed pump.

 

[gordiec]

Reporting back on this project -- I decided to replace the motor on my existing Super Pump instead of swapping it out for the WhisperFlow.

Mark’s analysis showed me that the Super Pump was moving more water that I had guessed, so I felt the $200 difference for a new pump wasn’t justified (not to mention that I would have had to change the electrical to 115 volts and do some plumbing). I ended up ordering a 2-speed, 1.5/.25 hp, 230 volt motor (A.O. Smith STS1152R) from American Best Pool Supply. They had the best price I could find and reasonable shipping – there were no problems with the transaction and I would buy from them again.

As far as the filter pressure goes, there is not much to report. On low speed the pump is moving water, but the gauge shows zero. Guess it is just not accurate at low pressure. On high speed it is about ½ psi lower than what the old motor was (it shows about 13 psi).

I borrowed a clamp-on amp meter and checked the old motor before removing it and new motor after installing it. The old motor was pulling 5.4 amps. The new motor draws 3.8 amps on high speed and 0.8 amps on low. Looks like I should save on the electric bill regardless of what I do.

Thanks for your help Mark, you saved me a bunch of bucks!

 

[mas985]

I'm glad everything worked out. Your new motor sounds like it is much more efficient than the old motor.