Going away...keep solar cover on or off?

[Macandfi]

Hi All,
We had a vinyl pool installed last year, and after finding this awesome forum I've been following the TFP method this summer. My question is this - we are going out of town for 2 weeks, and I was wondering if it was better to leave the solar cover on or off while we are away. We have a SWG and the water is balanced, so I wasn't going to have anyone do any pool maintenance while we are away. Any advice?


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[chem geek]

Welcome to TFP!

Either way should work but with the cover you will probably lose less chlorine to sunlight and will need to use a lower % ontime setting for the SWG so if you don't know what that normally should be with the cover on then you'd be better leaving it off. In other words, you don't want to under or over chlorinate so use the cover on vs. off that you are most familiar with in terms of the proper SWG setting. If you know both well, then put the cover on as that will not only extend the SWG cell life but will also help keep debris out of the pool. I assume that the water doesn't get too hot with the cover on -- that would be another consideration.

 

[Macandfi]

Thanks for the reply! I'm in the Northeast, so I had been keeping the cover on when no one was swimming because it just wasn't that warm, but now temps are getting warmer and I haven't used the cover for about a week. I'm inclined to keep the cover on because of debris, and also water evaporation, but I didn't know if that would be harmful. Should I dial the SWG down a bit? I'm operating the SWG at about 40% and running the filter about 8 hours a day.


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[chem geek]

I don't know how much your cover cuts down chlorine usage, but it could be by as much as half. So you probably should dial down the SWG but I don't know by how much. That's why I mentioned that it would be best if you already knew your chlorine usage with the cover on vs. off. Worst case, if the usage didn't get cut down at all and you lowered your SWG by half then the target chlorine level would be half. Likewise if you don't cut down the SWG time at all and the chlorine usage was only half then you'd end up with double the target chlorine level you have now. So why not split the difference and set your SWG at 30% and put on the cover. It may be higher or lower but probably not by that much for two weeks. I suspect the chlorine level will be higher than your target when you return but higher is better than lower in terms of preventing algae growth.

Do you have time to simply measure what happens with your cover on for 24 hours at the current SWG setting? By knowing the FC rise, output rating of your SWG cell, and pool size, we can figure out how much to lower your SWG output percentage. If you do this FC measurement, use a 25 ml water sample to get 0.2 ppm FC resolution per drop in the FAS-DPD chlorine test.