Even in the wintertime, if you circulate and don't winterize, you should strive to achieve good water clarity.
Your chlorine demand is low but you should keep a little free chlorine and stay on top of the PH. I'm not intimate with a Pentair SWG but I'd feel certain that it hasn't produced any chlorine since the water temp dropped into the 40's.

I'd suggest a gallon of bleach, adjust PH, and add some Super Blue water clarifier. Let the pool run 24/7 until it clears it up.

I don't know how large your pool is but unless it's pretty small I don't think that a few hours daily is enough filtration time.

Note, I'm a construction guy and not a pool service tech or familiar with winter running of cold almost northern pools so I may be off track.
I'm sure some others will offer you some higher quality advice.

See ya,
Kelly

While algae goes mostly dormant when the temps drop, it's not the only organic.

If you have a cartridge filter, I suggest avoiding clarifier as it will gum up the elements.

The salt cell, as Kelly said, quick making chlorine when the water got too cold.

Ignore the low salt warning for now. Cold water will cause the cell to read low salt, even though it isn't. It will come back when the pool warms back up.

Check and balance the chems. I am willing to bet you have a high pH and low alk condition.

Please note that adding any powdered chems will take longer to dissolve and longer to take effect.

The use of baking soda to increase the alk level will best be done pre-dissolving about 1 lb in a 5 gallon bucket or larger of warm water and poured around the deep end.

The use of muriatic acid (CAUTION MUST BE TAKEN!!!) to lower the pH is suggested. It's already liquid. Dilute it before adding and a couple of hours after having added the alk (filter on till the water is clear!)

Unscented Clorox bleach may be added directly, about 1 gal. per 10k. Test every few day. You will slowly see the chlorine level drop since the water is cold. When it drops to 1 ppm, add again. Clorox is made similarly to the way the salt cell generates chlorine, just on a different scale. Liquid chlorine in the pool stores is also, just more concentrated. Because of this, they all will raise a pool's pH.

Your pH will go up again. Watch it weekly. Aim for a pH of 7.3 this time of year to avoid scale formation.

Once the water is balanced and clear, then start reducing the filter cycle towards a 1/2 turn a day till the pool gets into the low 50's, at which time you will need to aim for 3/4 of a turn to 60 and then a full turnover or somewhat more above that.

Keeping the pool open year round is a year round activity. Just because it isn't being used doesn't mean it should be let go. It is hungry and needs to eat. It is an artificial life form, a pet, that is dependent on you for it's care.

Scott

Scott

Thanks gents. Good guidance. I've had a heavy leaf load here in southern NC and empty the skimmers on a regular basis. I added salt, but understand that good ol' fashioned clorox will be a good hold over until the water temps get up a bit.

Definitely a colder than normal winter here.

You mentioned two things that did not seem addressed yet. Low spped for a few hours and a large leaf load. Many leaves will leave organics as they break down. Perhaps thats why we call them "leaves".

I'm guessing your turn on the water is so low that it is not keeping up with daily breakdown of the organics. A good blast of chlorine with a bag or two of cal hypo will clear that up. Run some extra hours to get a good turnover anf then don't let is under turn from there moving forward.

Don't use cal-hypo in cold water. It doesn't readily dissolve. The use of Clorox is much more effective as it is already liquid and easily dispersed in the pool.

Scott

All great advice from Scott and Kelly. You can also go to Troublefreepool.com and read up in depth on talking care of your pool. I, along with many others have found that these 2 forums complement each other. Just my humble opinion, Hope this helps

Nctal, perhaps you were out of town, but we got about 3 inches of rain in one day. A lot of pools look like yours right now. Jump on it. Those that dont will have a huge mess soon.

Scott,

You may want to recheck the properties of CalHypo. The warmer the water, the slower the dissolve.

Got a reference we can see? I went looking and could only find references to granular size where the increased surface area of the smaller gain sizes for a given weight of product would disolve faster.

I remember learning in school that generally, due to lower temps, chemical reactions such as the dissolving and molecular regroupings to form new and different molecules, are slower because there is less energy available.

Cal-Hypo may very well be an exception. I don't know for sure. But since bleach is already liquid, dissolving isn't an issue.

Scott

Mike - Yeah, I had to drain some water out of the pool a couple of different times this year with all the rain we've been getting. Wonder why the water utilities still think we're in drought conditions here in the Charlotte area.

I've added three gallons of unscented bleach as suggested (one gallon two days ago and two more today in my ~40k gallon pool) and manually brushed the surface area of the walls and floor to knock some of that funk around so it can be filtered easier. My Polaris cleaner hasn't been very effective with the hose becoming less flexible in the cold, so that probably hasn't helped, either. With the added bleach and manual brushing, its already much less green than it was.

Thanks for the advice on here. As mentioned, this is my first winter with the pool - so some bridges are being crossed for the first time.

Just checking to see if your pool cleared? If not, I have some suggestions as green pools are my favorite; however, it will be a long posting.

We shut off all salt generators in the winter.