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Thread: Efficiency of SWG

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    Join Date
    Jun 2014
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    Edmond, Oklahoma
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    Efficiency of SWG

    First of all, thanks to all of you for the great advice I've received so far. This is my first pool and I'm a little over a week out from the initial fill. All things considered, putting the knowledge I've gained here into practice, my first few days have gone very smoothly.

    I'm curious as to how efficient SWGs are. I ask because of what's happened the last couple of days.

    Oklahoma is usually hot and dry this time of year. This summer has been odd however, and the last 3 days have been overcast, with moderate to heavy rain on 2 of them.

    My pool contractor set our SWG on an initial schedule of running 8a-5p with the SWG set at 65%.

    When I'd last done a FAS-DPD chlorine test (last weekend), I had FC of 7 with CC of <.5. I was pleased and had hoped the sun would help me get and keep it down to my current target of about 5 ppm while I am working at dissolving some CYA in the water. My final target is the lower end of the CYA/FC chart. I'm going for 60 CYA and 5 FC.

    Fast forward to this week. It rained all day Wednesday and Thursday. Nobody swam and there was no sun. The pump and SWG still ran on the 8-5, 65% schedule. I came home last night to find a large amount of red dirt in the pool. With the pool build just complete, I'm not able to lay sod until tomorrow morning. The rain had splashed a lot of mud onto the decking, then into the pool. To top it off, we'd had enough rain that we'd probably gained 3 inches on the water level.

    I spent about 90 minutes vacuuming the mud and skimming the leaves. It cleaned up surprisingly well (and quickly) for everything that was in there.

    I took an OTO test for chlorine and pH expecting the worst. I figured between the mud runoff into the pool, the dilution, and the trees near our pool that had also dripped a bunch of water off their branches, I was looking at low chlorine and potentially some evil growth. But the OTO test showed a darker yellow than I'd seen so far.

    So I broke out the FAS-DPD test, figuring there may be a lot of chlorine in there, but it's likely that all the mud and debris was going to leave me with a high CC.

    Last night's test,
    FC - 15.5
    CC - still less than .5

    So good news and bad. I am way too high on my FC, but it looks like I got the mud out before it caused a problem.

    Everything I've read here makes me think that a combination of the SWG running 9 hours each day on the cloudy days PLUS the rainy, overcast weather, combined with the fact that I have now dissolved a total of about 3# of CYA into my system, contributed to the pool not just holding, but increasing FC. I don't know my CYA level yet. I added the largest dose (2#) on Monday of this week and was going to wait until the end of the weekend to test for it.

    Does the logic on the high chlorine sound about right?

    For what it's worth, it's still a little overcast this morning, but should clear up later in the day. So I set the pump/SWG to run only from noon to 2 pm. I was going to run a more abbreviated schedule until the sun returns consistently over the weekend. Even then, I will still likely start ramping down from the 9-hour schedule my contractor has it on. I'll probably leave it on 65%, but knock an hour off every couple of days until my FC is holding in the 5 ppm range. Then I'll resume CYA additions until I can get it to 60.
    12,500 gallon, in-ground Grecian Rectangle (vinyl liner). Installed June 2014. Sand filter, SWG for chlorination. TF-100 test kit.
    Located in Edmond, OK

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    Mod Squad jblizzle's Avatar
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    Re: Efficiency of SWG

    Your logic sounds right. The cloudy weather and increasing CYA reduced the FC losses to the sun so they started to build up.

    As many people do not realize, SWG are not set and forget. You need to tweak them through out the year. Likely getting them set to maintain the FC during sunning summer days and letting the FC get a little higher during rainy days. Then in the winter (if you leave the pool open), you can significantly cut the SWG output and still maintain adequate FC levels due to cooler water, less use, less sun, etc.

    - - - Updated - - -

    As you know, we recommended a CYA of 70-80ppm for SWG, the reason being the SWG will need to run less and thus will prolong the life of the cell. 60ppm might be fine, but a little higher would not hurt.
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
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  3. Back To Top    #3

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    Jun 2014
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    Re: Efficiency of SWG

    Thanks Jason. I was basing my numbers on this chart http://www.troublefreepool.com/conte...art-slam-shock

    I was thinking the lower 60 CYA with a FC of 4 or 5 to start, since I've read so many horror stories recently about people who allowed their CYA to get too high. My thinking was shoot for the lower level since it's easier to add than to take away. That way, if I shot for 60 and got 70, I'm still good.
    12,500 gallon, in-ground Grecian Rectangle (vinyl liner). Installed June 2014. Sand filter, SWG for chlorination. TF-100 test kit.
    Located in Edmond, OK

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    Mod Squad jblizzle's Avatar
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    Re: Efficiency of SWG

    Sounds like a plan
    Jason, TFP Moderator
    18k IG pebblesheen pool, Hayward ProLogic P4 w/ T-15 SWG, Pentair 1HP 2-speed Superflo, Hayward 6020 DE filter
    500 sqft Heliocol solar panels, ThePoolCleaner, TF-100 test kit w/ SpeedStir
    Pool School + Test Kit + PoolMath = A TROUBLE FREE POOL
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    Re: Efficiency of SWG

    To test your FC loss I'd turn it off for a day or two to try to get you to the recommended level, do a test first thing in the morning (before sunrise) and do a test every night around sundown to see about how much you're losing daily to the sun. That way are you not only doing an OCLT to see if you're losing any at night to organics but you'll also be able to compute an average daily FC loss. With that, you might be better able to dial in your SWG to the optimum output to keep it at the recommended level.
    Pool size: 24000gal inground Vinyl-Taylor k-2006 and k-1766 test kits and-speed stir
    Intermatic P1353ME digital timer w/freeze sensor
    CircuPool Si-45 SWCG System
    Polaris 280 vacuum/Polaris PB4-60 boost pump
    Pentair IntelliFlo VS 3hp Pump--Pentair sand filter

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    Edmond, Oklahoma
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    Re: Efficiency of SWG

    Quote Originally Posted by timerguy View Post
    To test your FC loss I'd turn it off for a day or two to try to get you to the recommended level, do a test first thing in the morning (before sunrise) and do a test every night around sundown to see about how much you're losing daily to the sun. That way are you not only doing an OCLT to see if you're losing any at night to organics but you'll also be able to compute an average daily FC loss. With that, you might be better able to dial in your SWG to the optimum output to keep it at the recommended level.
    That's a good idea. It may get me to my desired setting faster than my plan.
    12,500 gallon, in-ground Grecian Rectangle (vinyl liner). Installed June 2014. Sand filter, SWG for chlorination. TF-100 test kit.
    Located in Edmond, OK

  7. Back To Top    #7

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    Peoria, IL
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    Efficiency of SWG

    We have a Compupool CPSC24 on an 18,000 gallon pool and run at 100% constantly during the summer. We close pool completely in Illinois winters. We have to add cya in the spring, but mine stays at about 85-90ppm. I have no idea where it goes over winter, but when I find that my swg can't "keep up" it is usually due to a lack of proper cya levels. My FC is off the charts right now as well (11) but it is going to be hot here the next week or so, it will drop. I do sometimes use liquid chlorine to boost when we have a high bather load or it is really hot for a long period of time.


    30x20 vinyl IG, Hayward SD60 with Pentair Dynamo 340219 2HP pump, Compupool CPSC24 SWG, Hayward H200FDN heater. APC automatic pool cover.
    Central Illinois

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