Question about calculating pump run time.

[shacke]

I never paid much attention to run time but I would like to.

I have a sta-rite filter, system:3 S8D110. It does not seem to be variable speed.

Looking on the filter, it shows a max flow rate of 106 Gal/min and a filtration area of 53 sqft for a filtration rate of 2 gpm/sqft. I assume flow rate is based on freshly backwashed and charged filter.

I have a 19,000 gal pool. Based on just the flow rate, that would be 3 hours to run through all my water once.

The run time will also depend on my heating needs and how much I want to rely on my SWG. Having said that, based on flow rate alone even 9 hours is enough to filter the pool 3x (!) - but I wanted to check in here and see if those other filter parameters might change this assumption.

Thank you!

 

[Eauclaire]

If heat distribution is important to you, you should run it during sun exposure. I run mine for only six hours with a replacement occurring every 2.5 hours. If I really want sparkling water, I have to run it 9 hours, which I do manually twice a week or so. If you are using a floating solar cover, you have to extend the run time, because surface water circulation is reduced as well as scouring in pool corners or pool floor at the deep end. I have to remove mine every 48 hours or so, to minimize biofilm formation, scrub and allow for longer filtration times.

 

[Richard320]

I get by with 3 hours a day. However, I don't run a SWG. You need to run it long enough with the SWG on to generate enough FC and keep the water clear.

If you maintain FC no problem with SWG on 20% for 9 hours, then you could try SWG on 60% for 3 hours. Or some other multiple; whatever your setting are. Just experiment and run things the minimum amount you can and maintain the sparkle. It will save electricity. $$$$

Pool School - Determine Pump Run Time

 

[BassTrix]

To calculate the flow rate with any degree of accuracy you'll need to calculate the headloss. Using headloss along with the flow table for your pump, you can estimate the actual flow for your particular application.

Headloss is also called back pressure. It's the resistance to flow that your pump must overcome. It's a combination of the losses on both suction and pressure side of system (from filter, pipe size, pipe length, elevation rise/fall, number of elbows, etc). The good news is that's it's easy to determine if you have a pressure gage.

The pressure side is generally easiest...it's just the PSI on your filter x 2.31 to convert from psi to Feet of Head.

Next, determine the inlet resistance. This will require a vacuum gage attached at the pump inlet side. Most pumps have a drain plug which can be used to connect the gage. Take this value (in psi) x 1.13 to get the suction losses in feet of head. If you don't have a vacuum gage, you can estimate suction loss as 1/3 of pressure loss.


Add these two values to get the total headloss. Use this number in combination with the flow charts for your specific pump to determine the flow rate for your system.

Your SWG should have a rating for how much Cl is generated in some given amount of time. It's been a long time since I've worked with heat exchangers, so someone else will have to chime in on that info, but this should get you a reasonable value for flow rate.

 

[Nesto]

Hi, am new to the forum and was just searching the swg thread about run time. 2 weeks ago I successfully completed an AA treatment for stains and pool looks like new but am concerned about too much chlorine and ph rise causing stains to return. About 3 weeks before the AA treatment, I had the variable pump installed; immediate savings but the salt cell died. So I just installed a new 1400 with sensor and dc and all is working fine. With my hi CYA and CH, any suggestions on run time to at least minimize the chlorine I am still going to be adding? Richard, I see you are in San Dimas, I'm in Pasadena so you know how crazy SCE is with the tiered pricing. I would like the swg to run at the low rpm setting in the day but the swg may not have enough flow. The variable has an rpm setting but I have noway to figure out flow rate as I had some awareness of what BassTrix is saying about back pressure and headloss. Do I just play with the settings on the pump to see at what point it shows no flow? That's what I am thinking and if so, trial and error it will be. btw, 47% water change not an option per wife instruction....

cl. 10-15 (I am still having loss from the AA I think so trying to keep it between here; doing overnight test with new cell tonight)
fc <.5
ph 7.2
TA 110
CYA 150 using 1/2 pool 1/2 tap water method
CH 600 probably more b/c i stopped adding drops
3200 salt is pretty constant

 

[BassTrix]

Nesto, your pump should have a table with various curves for different pump RPM. As long as you can set the RPM, you should be able to dial in the flow you want.