Gone For 7-Days, Have Questions/need Confirmation Please.

[LakeLizard]

I will be going away for 7 days and would like to know how or what to do to prepare our swim spa for non-use and no monitoring.

1. I assume lowering the water temperature to their lowest settings (80 degrees) will help in keeping the sanitizer level more stable?
2. We normally keep our FC level in both chambers at 3ppm
3. For the spa side which regularly is set at 102 degrees, it usually drops to .5 to 1 ppm in 24 hours. 1 person soaks for 15 min.
4. For the swim side which regularly is set at 89 degrees, I usually only add bleach every other day (5 oz) and usually stays between 2-3 ppm after the 48 hours. 1 person swims for 15 min each day.
5. So my question or concern is, should I add enough bleach to help it last for 7 days without use?
6. If so, what would you suggest?

For more clarification as to volume and such, it's in the signature.

I appreciate any and all suggestions on what to do to keep the water staying clear and usable upon return (after re-heating anyway).

Best Regards,

LakeLizard

[chem geek]

Yes, a lower water temperature will have the disinfectant last longer.

Your chlorine demand in the spa is 17%-33% but normally your 15-minute soak would use 2.7 ppm FC in 225 gallons so do you have an ozonator?

5 ounces of 8.25% bleach in 2045 gallons would be 2.0 ppm FC so since that's every other day that would be 1.0 ppm FC per day for the swim spa which sounds about right if it's not in direct sunlight (or at least not in summer).

If you don't have an ozonator, then you should be able to add enough bleach to last a week with no problem. At a lower water temperature of 80ºF your daily 24-hour chlorine loss should be no higher than 20% and that would create a 1 - 0.8^(1/7) = 79% loss so if you start out at 10 ppm FC you should end up with about 2 ppm FC. So that's what I'd do if I were you. As for your warmer SwimSpa you could do the same if you can lower it's water temperature though if there's sunlight exposure you may need to cover the SwimSpa with an opaque cover.

[LakeLizard]

Sorry, failed to mention there is an ozonator but am unsure it is functioning on the swim side (2045 gal) because FC has stayed elevated for days, while on the spa side (225 gal) I can be at 3ppm FC after a soak and 24 hours later it's maybe .5 (could be the fact it's 102 deg. also).

I also failed to mention the entire swim spa stays covered with a 5/3 insulated cover at all times except in use.

I think once I turn the heat down on both sides to 80 deg. and bring the FC level up to 10-15, it should be OK for these 7 days.

Thanks for your expertise ChemGeek, you are the man.