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IMO, I think the bigger point here is not to scare people with CD. CD is really only an issue when you are not able to maintain a chlorine residual after a shock. Chlorine demand in a hot tub is a very simple fix. Drain and refill. I respect your opinion and knowledge, Nitro, but I think you are making an issue out of something when it doesn't need to be.And Vinny is right, the heat of the tub alone will dissipate the chlorine faster than most people think.However, chlorine usage is a great thing to discuss, just as any other sanitizer would be. Personally, I still do not understand why the majority of the people on this board choose chlorine over bromine in their tubs anyway. Bromine is a much better sanitizer in a spa; pools, however, are the opposite.Like I said, I do appreciate your knowledge and willingness to help, but there are many other things that I think should be discussed before this.Thanks!
NitroI have spent the last 7 years in the municipal water treatment industry and believe me there is no such thing as "idle chlorine demand"
A tub left alone with no bathers will have an increasing demand even if you were able to maintain a perfect 1 ppm in the water.
There is simply no way to idle the chlorine demand without constant monitoring and adjustment to the free chlorine residual. Something that is just not cost effective in a hot tub. Chlorine demand is constantly changing due to the number of variables that effect it
NitroYou go with that I'll go with what I have learned in the last 7 yearsGood Luck
The time spent doing something means nothing, if you don't keep an open mind and continue to learn.
NitroI don't know what you do for a living but I do know what I do.Your information is wrongThere is no way you can idle the chlorine demand without using distilled water. It is just not possible
My information is correct. You may be misinterpreting it though.I don't know what you mean by "Idle the CD". CD does change depending on the amount of use. But if there is no use it will stay relatively constant (decreasing slowly, until either it hits the Baseline, or the Chlorine runs out).My point is if you use enough chlorine during and after use, the CD will go back down to the baseline faster, and stay there. If you're not using enough Chlorine, you will fall behind and your CD will keep getting higher over time, eventually becoming 100%. I've tested and confirmed this in my tub and others.Again, if you feel the urge to test your CD, let us know what you find. If you want to go further, test CD once. Don't use the tub. Then test it again the next day or two and compare the results. They should be pretty close. However the only way to know your baseline CD for sure, is to test it on a fresh fill.
CD does change depending on the amount of use. But if there is no use it will stay relatively constant (decreasing slowly, until either it hits the Baseline, or the Chlorine runs out).
My point is if you use enough chlorine during and after use, the CD will go back down to the baseline faster, and stay there. If you're not using enough Chlorine, you will fall behind and your CD will keep getting higher over time, eventually becoming 100%. I've tested and confirmed this in my tub and others.
Again, if you feel the urge to test your CD, let us know what you find. If you want to go further, test CD once. Don't use the tub. Then test it again the next day or two and compare the results. They should be pretty close. However the only way to know your baseline CD for sure, is to test it on a fresh fill.
On a fresh fill, after shocking, your tub will have a Baseline Chlorine Demand. This Demand is there because of "stuff" getting into the tub, outgassing etc. With no use this CD will stay CONSTANT, as long as you have Chlorine in the water. It will NOT increase. The Demand will stay the same, unless something CHANGES. i.e. People soak in the tub, a dog pees in it, the FC drops to zero allowing stuff to take over etc.
My CD is always 25% (has been for 5 months) when I'm not using the tub. I've tested this many times. I can shock my tub to 12 ppm FC. The next day FC will be 9ppm, next day 6.5ppm, next 5ppm, then 4ppm, 3, 2, 1.5, 1 etc. The FC drops at a CONTANT RATE with no use. Again, this is what I'm calling Chlorine Demand. Yesterday, my FC was 4 ppm, today it's 3. I just tested it.
Have YOU ever tested the Rate of Change of FC (i.e. Chlorine Demand)