Reading My Head Loss Curve

[cramar]

Finally found a head loss curve for my 1 hp pump.
I'd estimate total 1.5" pipe run (skimmer to return) is 20', looks to me like I'm off the chart and I'd estimate I'm at 85 gpm, my pool is +-9400 gallons so I'm getting 1 turn over in just under 2 hours......wow, seems high compared to other peoples numbers. I bought a 1hp pump with the anticipation of adding solar heat on the garage at some point.

I noticed last year that my pool temp was consistently lower than 2 of my neighbours even though they have the same amount of sunlight per day and we all use solar blankets. I was running my pump for a solid 10 hours a day, so that equates to 5-6 turn overs a day...no wonder my water quality was awesome, I'm thinking that all the pumping is cooling the pool down.

I'm thinking about cutting my pump run time down to a couple of hours in the morning and a couple of hours during the evening, 1 turn over each time, any thoughts on that?
I'm hoping the pump run time is still enough to clean the water (obviously I'll monitor with testing) but I'll get some extra heat thru less cooling action.
I'm also thinking my hard plumb job should be 2" pipe.

 

[JasonLion]

With 1.5" plumbing and a 1 HP pump, your dynamic head is almost certainly above 20'. Lots of things add dynamic head, starting with straight pipe length, every pipe fitting in the system, the main valve, the filter, the heater, etc. Calculating dynamic head is difficult, but it is possible to estimate it given a measurement or two. If you tell us what your filter pressure reads, and how high the filter pressure gauge is above water level, we might be able to guess at what your dynamic head and flow rate are.

There is a good article on figuring out what your ideal pump run time should be. The ideal pump run time depends on several factors in addition to the flow rate and pool size. The best way to figure it out is experimentally.

 

[cramar]

Maybe I'm reading the chart incorrectly, if I have 20' of pipe between skimmer and return the chart indicates I'm running +- 85 gallons per minute, my pool is 9400 gallons so I'm doing a turn over roughly ever 2 hours.

Or am I way off here?

 

[JasonLion]

20' feet of pipe doesn't mean that you have 20' of dynamic head. The vertical axis in that cart is "dynamic head", a measure of resistance to flow measured in equivalent vertical feet of water the pump could raise in a vertical pipe open at the top that would match the resistance to flow posed by your plumbing. Dynamic head is fairly complex to calculate and has only a limited and indirect relationship with the length of your pipes. There is a good introduction to this subject here. However, I warn you that it is fairly heavy reading.

 

[Bama Rambler]

For instance the multiport valve on your sand filter has about 10' of head. The eyeball on the return adds a good bit of head as well as the hole in the bottom of the skimmer. So, it's not just the length of your piping. It's every restriction, twist and turn in the system.

 

[cramar]

I read Hydraulics 101 recently - challenging read. I figured the easiest solution was a flow meter until I read that they have more error than I anticipated.

I see your points now, in addition to the multiport valve and eyeball I have 7-90 degree elbows, anyone wanna estimate gpm?

Maybe I should just do the bucket/timer test this summer.

 

[mas985]

Maybe I should just do the bucket/timer test this summer.

That is not very accurate either because it usually requires you to change the plumbing to do the measurement and that will change the flow rate.

I just realized that you have most of the information I need so here is an estimate of the pump's operating point: 54 GPM @ 39' of head

 

[cramar]

Thank you sir, your knowledge of hydraulics is remarkable!