question regarding GPM

[Uncle Vinnie]

I am trying to figure out the gallons per minute my pool pump delivers and cannot... this would be to better figure how long to run the pump.....

Here is what I have:

About 24,000 gallon pool

1 1/2 hp AO Smith motor, 3450 RPM 2" pvc Hayward grid filter, 60 sq ft - rated at 120 GPM.

Can I assume that number, 120 GPM?

thanks!

[kennybs]

All you have to work with are the numbers they give you, 24,000 gal. divided by 120gpm is 200 min. divided by 60 is 3.33 hrs. or 3hrs. 20 min. Your not building a watch so the numbers should be close enough to work with. The pump itself will have a different rating depending on head pressure and other veriables, and the filter rating is usually based on flow rate of efficency. Hope this helps. kenny b

[Uncle Vinnie]

I have come across a few other numbers if that makes sense.. one skimmer is

50 feet away, the other 38... surface area is 600 s/ft...

I have been going nuts trying to figure this out.. the reason is because for too many years, the pump has run 12 hours per day.. I want to do a minimum of one turn per day... also, the more it runs the more chlorine gets into the system.. so I was thinking of running it 6 or 7 hours per day... I was guessing it can't be at peak, there are other variables, so the number you got (I also got) might be too good to be true! (note, I have no idea how to figrure this stuff, it's a learning thing, hence my post!)

But I'd think, 100 GPM might be a little more conservative... and closer to mark?

thank you for your help.. are there other numbers you need that I might have and be clueless what to do with?!!

thanks again!

[e-mail] wrote:

[kennybs]

Having a pool years ago I believe my local pool place suggested running the filter for 4-6 hours a day for that capacity. That might be the place to check.

kenny b

[Uncle Vinnie]

Thanks Kenny... the original company, who was taken over, told me 12 hours a day! That was a nightmare as chlorine levels always ran high...

In reading around, the minimum is one turn... so my mission to figure out how gpm's in order to figure it out.. one person with a comparable, or slightly larger pool, same builder, runs his 8 hours per day....

Here is what I did.. simply took a large pail and using the waste setting (not backwash, simply excess water) I calculated a rough and messy 1.8 seconds for 3 gallons... 60 (secons) divided by 1.8 (my test unit) =

33.3333. multiply that times 3 (the gallons in my 1.8) - comes out to 100 gallons per minute - pretty close to the 120 gpm the filter is rated at.

So, I need to figure that as an absolute minimum... again, it was messy and I did not build any 'Mythbuster' equipment! Also, there may have been error in that it wasn't exact, delay in start/stop of stopwatch, lost water at the onset, etc. I am probably closer to 110 or even 120!

The pool is acutally in the mid 23k's, shy of 24k gallons... with that being said, I probably need under 4 hours to turn the water once.. running 12 hours a day turned it three times....

What I decided to now do: 4 hours in the early AM, pool cleaner going, that gets it ready for the day.... And, 4 hours, early evening, for a second turn - which will handle any dirt or chlorine lost due to heat/sun, etc....

I 'may' cut these back to 3.5 apiece as an absolute minimum.. far cry from the 12 hours per day it WAS running at, saving electricity.. and chemicals...

Does this makes sense in terms of flow to you?!

Thank you VERY much for coaching me along the way!

[e-mail] wrote:

[kennybs]

" I probably need under 4 hours to turn the water once." Your actually not turning the water over per say, as you would be from moving it from one vessel to another. Your basicly deluting it from impurities. You'll have to perform your own testing and compair your results until you yourself are satisfyed with the results. Chlorine is/was added independently in my time, I'm a little confused as to why this would have referance to filter useage. What am I missing?

kenny b

[Uncle Vinnie]

[kennybs]

Thanks, makes sense now.

kenny b