# Thread: Pump questions

1. ## Pump questions

I have a 1 1/3 hp pump that has rpm 3450 rpm. I am trying to figure out how long it takes to cycle 28000 gal. I also would like to know if any of you have a timer on your pump. I think I gave you all the info. The pump is part of a Hayword pump/filter.

If I missed something, Im trying to post this between phone calls at work

As always thanks in advance

2. You might start with this sticky and if you have any further questions, I will be happy to answer them.

3. Unless you know how many amps the pump is pulling and have a pump curve it will be difficult to come up with a good answer. The GPM is going to be a function of the pressure drop across the system.

4. I will be getting all of the info off the pump today after work. Also, I do know all of the pipe above ground is schedule 40 marked with a "1 1/2", I assume that is I.D. I will also be posting a picture of the pump layout. And I will also be estimating the length of the pipe runs between skimmer, return and the pump.
My wife is a mechanical/electrical engineer and she is excited about working on this problem for me

As always, Thanks In Advance

5. Its not just the physical lenght, you have to add the equivalent lengths for every elbow, tee, valve, fitting -- and these things are typically more total length than the straight run of piping.

6. I will have to make a few assumptions without digging up the pool area. Is it standard to use straight or direct runs. The skimmers appear to be straight runs because of the relative position to the filter. I know this is confusing without pictures or a diagram, I am hooping to get that done today.

7. You can estimate the return head loss from the PSI reading on your filter (2.31 * Filter PSI). With 1 1/2", suction head tends to be on the high side as well so usually I use an estimate of 3-4 * Filter PSI as approximate total head loss. This tends to be a better estimate than trying to add up all the fittings and pipe lengths. Anyway for flow rates and turnover, you don't really need to be all that accurate.

8. ## I think you just made my day

OK, a possibly dumb question. Should I backflush and clean and rinse and then take 3-4* gage psi?

9. Yes, you want the clean filter pressure.

10. Found this on the stickey that was in a response to my initial question and I want to make sure I am looking at this right...

Return Head Loss(2.3*Filter PSI) + Suction Head (3-4* Filter PSI) = Pump Head ( and this is what I look at on the chart.

I really appreciate the help.

11. The formulas for head loss are:

Return head = filter PSI * 2.31
Suction head = vacuum (in mg) * 1.13

Most people do not have vacuum guages so as an approximation, I usually use 1-2 * filter PSI for the suction. For most pools, this works out ok. Suction head is usually 40%-80% of return head.

So the TOTAL head loss is 3-4 * Filter PSI. Normally 1 1/2" plumbing is closer to 4 * filter PSI.

12. OK, so does that number (4* Filter Pres) Total Head Loss.....is that the number that I use to cross on a graph....

This could be an illustartion of why I switched magor from engineering to management

13. OK, I think I finally came up with the right question......is Feet of Head the same as Total Head Loss? And on the Head curve chart, iis it a direct translation to plot a 1 1/3 hp in between the 1 hp and the 1.5 hp pump?

As always, thanks in advance and thanks for your patience

14. Total Head Loss is measured in feet of head. There are various other "head loss" figures, also measured in feet, that get totaled to give you Total Head Loss.

You want to find the pump curve for your specific pump, approximating from other pumps will be much less accurate.

15. Originally Posted by Valkyrie
OK, so does that number (4* Filter Pres) Total Head Loss.....is that the number that I use to cross on a graph....

This could be an illustartion of why I switched magor from engineering to management
Yes, 4 * Filter PSI should be close to the Total Head loss that you would use with the pump curve. It will probably be an upper limit on head which means a lower limit for your GPM and an upper limit on turnover. So it should be a somewhat conservative estimate.

16. ## Enough info for equation

OK, I have more info on the pump and :

Hayward/A.O. Smith Mod K48M2xxxxx bacause K48M2111A2 got me no where

1.5 HP
1.3 Service Factor (looking around, I saw one site had you take HP x SF = true HP)
19.4/9.7 amps (I assume that is start/run, unless I have a 2 speed and dont know it)

Filter press before backwash/clean: 15 psi
after : 10 psi

4 x 10psi = 40 head in feet

using the chart in the stickie for 1.5 hp = appx 130 gpm (which does not sound right)
using the stickie and hp x sf = 1.95 hp = appx 155 gpm ( which seems even more not right)

Any thoughts

17. The 1 HP motor from the Hydraulics 101 sticky is a reasonably close match to your pump, 1.9 brake HP compared to your 1.95 brake HP. That still gets you 108 GPM if your head estimate is right.

For a better estimate you can go to the Hayward web site and look at their different pumps to see which one looks the most like yours and then you can look up the pump curve for your specific pump.

The two different amp ratings are probably for 115 volt wiring vs 230 volt wiring on a single speed motor.

18. The 19.4/9.7 amps is most likely telling you that the motor would draw 19.4 amps at 120VAC or 9.7amps at 240VAC.

19. http://www.haywardnet.com/pdfs/SuperPump-05.pdf

Now with the 1 1/2 hp and the 40 feet of head, when I cross the graph on the 1.5 hp is that telling me what I should have or what I do have.

And how does that help me on my turn over

I know I am a bit of a rock on this subject, but I do appreciate the help

20. Assuming your flow is around 100 GPM, see my previous post, and calculating for a 28,000 gallon pool, it takes 280 minutes per turnover (a turnover is pumping the same number of gallons as are in the pool). 280 minutes is about 4 hours and 40 minutes. Looking at it another way you are getting a little over 5 turnovers a day (which is a lot, 3 is more common).

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