Am I Doing Something Wrong?

[DT835]

After a year of frustration, trying to keep up with an ever increasing chlorine load and nothing but bad advice from my dealer, I tried the TFP Dichlor to Bleach method.

The results have been nothing but amazing. Two months in and the levels are all rock solid and the water is crystal clear. Thank you to all for all the great advice.

My question has to do with shocking or lack thereof. I bring the chlorine level up to 6 ppm every two days and by the time I am done with the hot tub on the 2nd day, the FC is about .5 so I bring it to 6 and repeat the process. The CC has never gone above .2 and the water has always appeared pristine. I should also mention the hot tub is a Jacuzzi J-365 with UV.

I have yet to shock the hot tub. Am I wrong?

 

[RDspaguy]

hot tub is a Jacuzzi J-365 with UV.

There is your answer. Ozone and UV both destroy chloramines and excess chlorine in the water. CYA helps some with the uv (not much) but not a bit with ozone. Test daily for a few days to see if your fc is .5 after 1 day. It probably is if you have ozone/uv

 

[UKjames]

UV and ozone are what I think might be referred to as “snake oil”.


What matters is your CYA level. Once you know this the pool math app will tell you the level of FC you need. If you maintain your FC to CYA ratio you’ll never need to “shock” the pool.


if you let the ratio go out of recommended range then you might need to SLAM.

In order to measure your CYA and FC you need a proper test kit like the Taylor 2006C. Pool store or test strips are no good.

 

[RDspaguy]

Not snake oil. Just an oxidizer, like a shock. It burns off cc and fc more slowly. It does not mean you don't need to add chlorine, which seems to be the mistaken impression many people have. It has been used for decades to eliminate sanitation byproducts in municipal drinking water treatment.
UV radiation is also a proven destroyer of pathogens, especially at the levels in a UV unit, and will burn off chlorine. That is why you use CYA in an outdoor pool.
The key to the effectiveness of either is output and duration. On a Jacuzzi Premium you likely have a 24 hr circulation pump and get 24/7 uv/ozone on a good injection system. A spa without a 24/7 circ pump will see little effect from uv/ozone. Older tubs not plumbed with mixing chambers and long pipe runs on the ozone return would eat covers like cheetos.

 

[DT835]

Thanks for the responses.

I never did put much stock in the UV system. FYI, the CYA level is 30 and I do use the Tayulor K2006 to measure my levels.
TA is 70
CH is 130
CC is never above .2

So am I doing harm to the water by letting the FC go from 6 to .5 and never shocking the system?

 

[RDspaguy]

If your uv is a combo uv/ozone (many new ones are) and on a 24/7 circ pump then the ozone is the shock, and the reason your fc drops so fast. That is what ozone does for you, and how it provides a "low chlorine" spa. It doesn't mean you use less chlorine, but that it gets rid of it between uses so it is "low chlorine" when you open it, in spite of having added chlorine after use the day before. That's what I recommend, by the way. Hit it with 3ppm plus 2 ppm per person after each use. You should have nearly .5ppm fc and 0 ppm cc by the next day.
I've read the "slam" process and, frankly, I would drain and refill before going through all that on a spa.
I do recommend ahhsome spa purge at least once a year, if not at each water change, which should be every 3-4 months.

 

[UKjames]

Isn’t the problem that there is no way to test the uv/ozone. So you don’t know how good your sanitation is. whilst it’s a spa so you can drain to get rid of any greenness, you might not want to take the week off if cryptosporidium pays a visit.


seems a bit silly to me to add chlorine and then apply uv to it to break it down - better to turn the uv off and let the chlorine be used up fighting bugs/algae.

as to whether letting your fc drop to 0.5 ie ok- we’ll it’s below the recommended ratio to your cya level but you have uv/ozone doing some oxidation so it might be ok but it might not - as above.
I’m no expert though.

 

[RDspaguy]

Isn’t the problem that there is no way to test the uv/ozone.

That, and no significant residual. That's why it is not a sanitizer. But in a spa with a closed cover there is little chance of new contaminants, unlike an open pool. You are the primary source of contamination. Since you add chlorine after use to destroy pathogens then close the cover, it will keep it clean for weeks of non-use. But it's main purpose is to shock the cc and extra fc left over after all pathogens are destroyed so you have no chemical odor and, if chlorine sensitive (which many think they are but is actually extremely rare), a low fc at the time of use. This way you are not guessing on contaminant "load", you can add enough chlorine to ensure complete sanitation and not have 10ppm chlorine and a green cloud of chloramines when you open the cover the next day.
As for not needing to shock based on cya, I am unclear how that might work, but in an open pool you have alot of uv exposure and that does deplete fc and cc. Stabilizer (cya) is like sunscreen for chlorine, but the balancing act of fc/cya keeps you from getting full uv protection without rendering your fc useless as a sanitizer. Heavy bather loads (such as public pools, waterparks, and my brothers house) still produce heavy cc whatever the fc/cya balance. It's all about contaminant levels. And spas are heavy bather load with 1 person in them.
I should also mention that I like Nature2 with my ozone (the crowd gasps...). Another "snake oil", according to this forum, but effective over long timeframes (like overnight) in a closed system (like a spa with a good cover) against many pathogens including chlorine resistant ones like cryptosporidium.
In my personal experience (26 years fixing in your backyard and refurbishing in mine) this is the way to go. I have owned many, many spas (for a few months at a time) and have tried it all over the years. This system is the most trouble free and easy one I have found, and I won't keep a spa without a good 24/7 ozone system for my personal use. I have kids in it for hours each day, and would spend more time and have more periods when they have to wait because I just shocked without ozone.
The problem, I think, is that both are marketed as "low chlorine" and were once marketed as chlorine replacements. And while 99% will have no serious problems with little or no chlorine or mps under normal private spa use, the potential is there for very serious problems. So regulations say you still need a sanitizer or mps, and tfp does not contradict regulations. But many people still do it and recommend the way that has worked for them for years. And most people won't have any trouble, but who wants to be that .01% with a flesh-eating bacteria?