help newbie with SWG in winter

[chem geek]

Just ignore my question about the chlorine being too high and not showing up on the test. That's probably not happening if the pool guy was doing the test. I was just concerned if you 1) added more chlorine than you thought you did and 2) bleached out the test you made. Since that's not what happened, ignore my question.

I don't think you need to run your heater to see if the SWG goes back on. The shutting down of the SWG at colder temps is normal (as Mark said above).

As for what to do in the winter, you have essentially two choices. You can add bleach, probably not more than a large dose once a week since it SHOULD last that long during the winter (with a cover it would last MUCH longer). Or you can not add any chlorine and risk opening your pool next season to algae -- which is just a risk and not a certainty. There are pictures of algae under ice somewhere on this forum so cold temps do not guarantee that algae will not grow, but it is far less likely (usually algae doesn't grow below 50 though some users reported small growth in the 40's). If you get algae, then you'll need to kill it at the start of the season as seen in this post which shows opening in the spring with algae and using bleach alone to kill the algae in less than a week. With added chlorine bleach AND an SWG running 24/7 (when killing the algae), it should get killed faster, possibly in half the time or less. Oh yes, there's a third alternative and that would be to not add bleach regularly, but just add a large dose of PolyQuat 60 algicide which will help to inhibit algae growth. It might not last the winter, but would certainly help.

As far as thinking that an SWG means you don't have to do any maintenance, that simply is not true. You still need to check your pool water chemistry. During summer use, the chlorine demand changes throughout the year based on bather load and sunlight so you have to test chlorine and adjust your SWG output accordingly. Once your SWG is set so that the chlorine level is relatively stable, you won't have to check it as often, but you still have to check it at least weekly. You probably have to check your water more frequently than that because the pH will rise and you'll need to add acid to compensate and that may be more than once a week. Your pool sides and surfaces still need brushing, either manually or by a pool sweep that climbs walls (well, LIGHT brushing for your vinyl liner and I'm not sure automated pool sweeps do that well with vinyl). Maintenance simply does not go away with an SWG -- only the regular daily or every other day addition of chlorine goes away, that's all (though that's a lot!). During the winter things are easier and yes, you probably don't need to adjust most chemistry parameters, but if your SWG comes back on for some reason, you'll need to check chlorine and pH, at least.

My own pool (with no SWG) has a cover on it and I only have to add chlorine about once a month during the winter and could even just dump more chlorine in and go two months without checking if I had to. All other water chemistry parameters (pH, TA, CH, CYA) are rock solid and do not change at all over time (except CYA might drop -- I'm checking on that this winter). My water temps are between 45 and 50. That's why I was surprised that your chlorine didn't last just a few days after "shocking" which implies a high chlorine level when you shocked. That is VERY unusual in the winter time, even without a cover.

Richard