Pump turnover time, is this correct?

[rowdy93]

So the new pump, filter, ect. is now installed and wanted to fiqure out how long I needed to run. YES, I know there is a topic in pool school that is "figuring out pump run time" but that seemed to be running a big circle to get to the same point as a straight line.

I have the whisperflo wfds-24, running on low my PSI is 0 @ 3in hg
RETURN DYNAMIC would be 2.31x0psi+3psi=3
SUCTION DYNAMIC would be 1.13*3in hg=3.39
So my head on low would be 6.69 or just round to 7, so with my pump curve I would be moving 40GPM or 2400GPH, so I can turn over 22K Gal in 9.2HRS on LOW.

Running on high I'm at 13PSI @ 7in hg
RETURN DYNAMIC would be 2.31*13PSI+3PSI=33.03
SUCTION DYNAMIC would be 1.13*7in hg=7.91
So my head on high would be 40.94 or 41, with my pump curve for high I would be moving 80GPM or 4800GPH, so I can turn over 22K Gal in 4.6hrs.


The numbers do seem correct to me, they are directly proportional to ea other. The flow is what doesn't seem correct, when I look at the fountain or feel the returns on low, it just doesn't seem like that is moving 40GPM.

I do alot of automotive work, so I already had a vacuum gage, but for those who don't and want to do this go to harborfreight or www.harborfreight.com. I think the gage was aroun $15 and actually had the NPT adapters to fit my pump basket drain

Please shot me your inputs

Seth

 

[Richard320]

You're getting too technical for me...I just moved valves around and timed how long it took to move a few inches out of and then back into the spa from the pool.

40 GPM should be easy to check...hook up some type of hose adaptor and see how long it takes to fill a 5 gallon bucket. It shouldn't take long, have someone else stand by the switch while you hold the hose!!

 

[rowdy93]

You're getting too technical for me...quote]

Actually I'm not!! This was just the info that i pulled from? Mark I beleive?, in his post Hydraulics 101 have you lost your head. You can easily know your GPM by having your pump curve and two numbers, one of them is provided for you. So pump curve, filter psi and vacuum= knowing your GPM. Here's how you do it

Return Dynamic Head=2.31*filter psi+3psi Mark says the added 3psi is because generally the pressure gage is 3ft above the pump.
Suction Dynamic Head=1.13*Vacuum measured in In Hg

Add your Return and Suction Dynamic readings and that equals total head. Plug your total head into your pump curve, scroll across until you meet the curve, scroll down and you will have your GPM. Once you have your GPM, you can fiqure your GPH and get your true and accurate turnover times.

Anyone please correct me if I'm wrong. I was doubting myself only because what is coming out of my returns didn't seem like it could be moving 40GPM

 

[Bama Rambler]

How many returns do your have and what size are the eyeballs?

I doubt your return pressure is 0. It's probably close to 1 psig if not more.

 

[rowdy93]

2-1.5in returns and then the feed for the polaris. I would guess its about 50% less then the 1.5in returns. Currently only one eyeball, other is removed for fountain. PSI is now 1 on low speed, but starting PSI was 0

 

[mas985]

First, I would not trust pressure and/or vacuum measurements at low speed because the gauges are not that accurate at the low end of the range. Plus, when the filter pressure reads 0 PSI, it could actually be a negative value but the gauge does not go below zero. This is why it is best to make measurements at high speed and use the affinty laws to predict the flow rate at low speed which is 1/2 of high speed.

However, if the plumbing changes with flow rate, then determining the low speed flow rate using the affinity law may not be very accurate. About the only thing that can change the plumbing with flow rate is a check valve. When flow rates reduce, the check valve can partially close increasing the friction loss of the valve.

 

[noaliasneeded]

Just need a little clarification, so my apologies to the OP. If my Total Dynamic Head is 36.32 (11psi & 7hg), and the Hayward chart on my pump (SP3210X15) shows 100 GPM @ 40, I could safely use that GPM since the chart doesn't go below 40? So the water in my 14K gallon pool is being turned over every 2.33 hrs? I feel like I'm missing something. Thanks

 

[rowdy93]

Just need a little clarification, so my apologies to the OP. If my Total Dynamic Head is 36.32 (11psi & 7hg), and the Hayward chart on my pump (SP3210X15) shows 100 GPM @ 40, I could safely use that GPM since the chart doesn't go below 40? So the water in my 14K gallon pool is being turned over every 2.33 hrs? I feel like I'm missing something. Thanks

Assuming your math is correct on your head loss, I didn't check it, you would use the 40ft for your loss. I looked at your curve and looks like you got it all correct. So yes you would be turning over your 14k in 2.3hrs. In my opinion, your pump is way too big for your pool. Not sure if you have a spa or not, but if not you don't need that much flow. Jason and Mark had told me, at beginning of my pump search, you want to have a turnover of about 8hrs and slower is more effecient. Although, I'm new to TFP and am not the expert

 

[rowdy93]

First, I would not trust pressure and/or vacuum measurements at low speed because the gauges are not that accurate at the low end of the range. Plus, when the filter pressure reads 0 PSI, it could actually be a negative value but the gauge does not go below zero. This is why it is best to make measurements at high speed and use the affinty laws to predict the flow rate at low speed which is 1/2 of high speed.

However, if the plumbing changes with flow rate, then determining the low speed flow rate using the affinity law may not be very accurate. About the only thing that can change the plumbing with flow rate is a check valve. When flow rates reduce, the check valve can partially close increasing the friction loss of the valve.

Well my gauge was slightly off of zero, about one or less, so I know it wasn't negative. The values that I pulled from high and low speed were proportional in the GPM, which they should be. My math came to 80GPM High and 40GPM Low. Even though taking measurements at low speed worked for me and seemed accurate, I do agree that it could not be accurate and gauges aren't dead on.

Thanks all to your inputs, I feel comfortable saying my turnover, on low, is alittle over 9hrs. All it took was alittle math and about 10 minutes to get my fiqures from the pump and filter

 

[noaliasneeded]

Thank you. The 1.5 HP was what the builder picked when the pool was installed last August. I run it from 11am to 5pm with the SWCG set at 45% and have had absolutely no problems keeping the water crystal clear.

Thanks again.

 

[mas985]

I have a hard time believing you only have 36' of head with a 1.5 HP pump. What size is the plumbing?

 

[noaliasneeded]

Plumbing is 2"

 

[rowdy93]

Thank you. The 1.5 HP was what the builder picked when the pool was installed last .

Seems that builders picking oversized pumps is a common thing

 

[mas985]

Plumbing is 2"

36' of head is pretty low for 2" plumbing. You must have a combination of multiple and/or short pipe runs plus very few fittings or valves.

 

[noaliasneeded]

Plumbing is 2"

36' of head is pretty low for 2" plumbing. You must have a combination of multiple and/or short pipe runs plus very few fittings or valves.

The equipment is 30' from the pool, which is 14' x 30'. All of the returns (3) are fed from the same side of the pool. I can't recall if they are all fed from a single 2" run branching off to each return, or a dedicated run to each one. You are correct that there are not alot of fittings or valves.