Is it normal to add Chlorine daily? Temperature? CYA?

[MDouglass]

So, I feel like I should know this by now, having owned my hot tub for 3 years but I admit I am still learning to master water chemistry. 

I have a master spa hot tub that I keep at around 103 degrees. I purged the water about 2 months ago and used Ahh-Some prior to draining. My water is clear and I don't have any rings around the sides. I can't understand why Im going through a tub of the chlor-brite chlorine so quick. In my first year I added chlorine maybe 1-2 times per week, but I kept the water at 97 and only turned it up to 103 or 104 when i wanted to get in. Now we use the hot tub 5-6x a week, so we don't adjust it down and up that often.  Is the higher temp consuming the chlorine more rapidly or is there another problem? I also shock the tub with a non-chlorine oxidizer after each use, which accounts to about 5-6 times per week.

All my readings are fine except for Cyanuric acid (CYA) level which are reading very high over 100ppm. It seems that after a month after refilling and with almost daily use that CYA number exceeds 100ppm...Should I change up what I am doing? How can I use less Chlorine ?

 

[RDspaguy]

You can use less by using less. A CYA much over 30 binds up the chlorine. Your chlorine granules are dichlor, which contains CYA. So every time you add chlorine you also add CYA. Dichlor should be used sparingly in a spa, except in special circumstances. If you want to maintain a residual, tablets or liquid is the way to go. 

 

[castletonia]

Chlorine dissipates faster in water that is above 97 degrees.  Chlorine also doesn't last a long time in the water so its not uncommon for chlorine to be gone with 24-48 hours.  Also, if you have an ozone and don't use the hot tub frequently, the ozone will oxidize off any extra or residual chlorine faster than it would dissipate on its own without ozone.

[MDouglass]

Thanks for the posts about using bleach.  Does using bleach in the water have any affect on skin? My wife was sensitive to bromine when we first got the tub and we exclusively use chlorine now. Does liquid chlorine last longer? If  they both contain Dichlor why would that be the case?

 

[RDspaguy]

Bleach, or liquid chlorine, is sodium hypochlorite. It has no dichlor or CYA.

If your wife is sensitive to bromine she is also sensitive to chlorine. And by that I mean she is not sensitive to either. If she were, she would have known long before she was your wife. Municipal drinking water regulations require a detectable level of chlorine, up to 4ppm allowed. Trust me, if she was sensitive, she would know.

Dichlor is ph neutral in solution, so by using it you are not getting constant ph drag from a floater full of acidic sanitizer (Bromine ph4). Liquid chlorine is high ph, so will also have to be balanced much more frequently than dichlor to avoid irritation.

I personally use dichlor, specifically 1 tsp plus 1/2 tsp per person after each use of the spa. I drain and refill at around CYA 50, which is about 2-3 times per year for me. I do not maintain a chlorine residual. I have an ozonator, so rarely shock. 

In an outdoor pool (or uncovered spa) you need a residual (constant level of sanitizer) to deal with contaminants (windblow microbes, dirt, leaves, acorns, bird poop, grass clippings, etc...)

In a spa that is covered 23 hours of each day, it is not so important. The only contaminants that enter the water are the ones you bring with you. Shower before use, and you cut those down by 90%. Hit it with a bit of chlorine after use to destroy what you brough it, ozone gets rid of the chloramines and residual chlorine. And tomorrow when you open the cover you have virtually chemical free clean water. If unused, a weekly treatment of dichlor is needed.

Mineral purifiers, such as spa frog or nature 2, are a good addition to the program. These use silver and copper to kill some microbes and interfere with the cell division of the rest. This technology dates back to pre-colonial times, when they would put a bit of copper and a silver coin in fresh water barrels aboard ship to keep the water from getting nasty. They couldn't have discovered America without it.