SWG Doesn't work in winter?

Aug 12, 2015
1,683
Cypress
A friend that built their own gunite pool in 2012 told me that the SWG doesn't work in cold weather. He said he got something for $80 and uses pellets to maintain balance during the colder months of the year because the SWG can't produce enough chlorine.

Does that sound right?
 
Most SWGs have a "cold water" cutoff around 50F because the cell will not efficiently produce chlorine. Once my water falls below 55F, my IC40 does not operate. At that point I manually chlorinate with bleach as-needed. In fact, many people will go as far as to remove their cells in winter and replace them with straight tube (Pentair sells a specialty tube with the proper connectors just for that purpose) to protect them from potential freeze damage.


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What JFN says about the SWG not working with lower water temps is true.

TFP recommends just using chlorine during the winter. Trichor pucks and granual chlorine pellets contain Stabilizer, so you have to be careful with it so your CYA doesnt get too high.

During winter I only have to add maybe 1/2 gallon or so of liquid chlorine to my pool every week or so. With the water below 55 ish, algae doesnt grow well at all so the chlorine demand in winter is much lower than it is in warmer seasons. And also there isnt as much UV from the sun to burn off the chlorine. So its really not a very time consuming task to maintain chlorine levels in winter time.


A friend that built their own gunite pool in 2012 told me that the SWG doesn't work in cold weather. He said he got something for $80 and uses pellets to maintain balance during the colder months of the year because the SWG can't produce enough chlorine.

Does that sound right?
 
That is correct, SWG does not make chlorine when the water is cold. It can also give you a low salt error. Don't fall for it and don't add more salt like I did the first year with mine.

Chlorine usage is very low in cold water. I target 10 ppm FC so I can test PH. 121 oz of 8.25% bleach adds 4 ppm to my pool. When it drops under 10, I test PH and add another jug. Less than once a week maybe even less than every two weeks, I can't remember. It doesn't take much.
 
Thank you! I asked one of the builders I was interviewing about this and he said it would work fine in the winter. I guess I should cross him off my list. :)

Well, just to play Devil's Advocate here, my SWG does "work" fine in the winter ;) It checks the salt level and the temperature and, when it's too cold out, it tells me it's not getting out of bed to make chlorine for me....so, it is "working", technically :razz:

The fact is, in the winter (and I imagine this is true in Cypress, TX), your pool will be open but too cold to swim in (without a wet suit). As such, the chlorine demand will be incredibly low. Below 60F, algae reproduction rates are minuscule and chlorine demand is basically driven by sunlight (UV) and whatever happens to blow into your pool. So, if freeze damage is not an issue, then you can leave the salt cell running and just manually chlorinate as-needed. For me, my pumps run a minimal amount of time in the winter, mostly for cleaning and if the freeze protection kicks in. My actual chlorine demand, if I have to do it manually, is ~ 1 quart of 8.25% bleach once per week.

So don't overthink the SWG thing too much. They work fine all year round in warm southern climates and there's not much to worry about over winter with them.
 
A friend that built their own gunite pool in 2012 told me that the SWG doesn't work in cold weather. He said he got something for $80 and uses pellets to maintain balance during the colder months of the year because the SWG can't produce enough chlorine.

Does that sound right?
Sounds right to me as I think it is hard to generate chlorine when your pool is a block of ice as happens up here in Canada!
 

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Once the water is too cold for the SWG to work, algae growth is nil and you aren't going to be swimming, so whether the water is safe becomes a mute point.
 
What if I have a heater? Seems obvious, but no body commented on it earlier...

If you heat the water above 55F and the cell registers that temp on it internal temperature sensor, then it will start to produce chlorine.

For example, I can run my attached spa in January (it's kind of cool to see the water vapor float off the surface) and get it up to 95F. The SWG, in spa mode, will activate and generate chlorine (usually 1/20 of set point, max of 5% output).


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So if the OP has a heater in the quote, then the SWG comment by the PB might be valid. Just not well explained.

I suppose so. But I don't know many people that try to heat their pools with a gas heater in the winter time. Unless the pool is designed from the beginning with insulated PVC piping, an insulated gunite shell, some kind of solid cover and an enclosure, trying to heat 10,000+ gallons of water in the dead of winter to swimmable temperatures is an exercise in futility.....and making the gas company VERY happy ;)
 
Is the OP in Florida? Many there do keep the pool up to temp year-round, but a heat pump is the usual choice if your going to do that.
 
We have very mild Winters and pool water temp tends to stay in the 50s. I found my SWG would not generate in the mornings but would run most evenings unless we'd had a really cold day. I switched pump run start time to 4 pm and didn't have to use bleach.
 

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