gone for up to a month question

surferbum

LifeTime Supporter
May 18, 2013
69
North Scottsdale
I plan to be gone for up to a month at a time from my house which has a Cal Spa Bel Air spa. A friend (who has a spa too) told me that his method in a similar situation is to shock the spa prior to leaving; turn off the spa; shock the spa on his return one month later. It seems to work for him. Are there any others who use a similar scheme? Any reason not to do this? :?:
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
For a spa, it is important to turn it off as you suggest. Otherwise, the circulation pump alone is enough to heat the spa perhaps to 80ºF or so which will be warm enough to deplete the chlorine too quickly. If you let the water cool off to a lower temperature, the chlorine should last longer and you may get it to last the month.

You can do a simple test before you leave where you check the 24-hour chlorine loss in the spa. Let's say that was a 5% loss of FC. Then 30 days would be 0.9530 = 0.21 or 21% so if you started with 10 ppm FC you should have around 2 ppm FC after 30 days. However, if you have a 10% loss of FC per day, then you would have 0.9030 = 4.2% so 10 ppm FC would end up with 0.4 ppm FC so not enough. So you can see how sensitive the situation is to the daily chlorine loss rate.
 

surferbum

LifeTime Supporter
May 18, 2013
69
North Scottsdale
Thanks for the comments. I use bromine (Leisure Time) for the spa. The popular shock products with favorable ratings on Amazon for example are:
  1. Oxy-Spa Non-chlorine Hot Tub & Pool MPS [/*:m:ggzxtzj2]
  2. Shock Leisure Time RENU2 Renew Non-Chlorine Shock[/*:m:ggzxtzj2]

Oxy-Spa has a better per/use price and is claimed to be as-good-as Leisure Time's shock. Anyone have an opinion or other recommendation?

Is there anything I should take into account due to the chlorine shock and bromine usage during spa use?

Thanks.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,083
San Rafael, CA USA
If you have been using bromine for a while and either created a bromide bank initially by adding sodium bromide or if you have been using bromine tabs, then you could probably increase your bromine levels by simply adding bleach rather than using expensive products that are called "shock" but that are just oxidizers (usually chlorine or MPS).

You should still figure out your 24-hour bromine loss rate (with no bromine floater).

Does your spa have an ozonator? If you have a bromide bank and an ozonator, the ozone should create bromine for you and could maintain a bromine level. However, if you lower the temperature, the bromine level might get too high if the ozonator produced bromine quickly but the bromine got used up slowly. A high bromine level could deteriorate your spa cover faster (as well as pillows or other components of your spa).
 
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