CYA high...and bleach how much?

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C

Carski78

Member
May 3, 2020
7
London
2nd post - 2 weeks in on first hot tub ever...learning fast! But still blinded by the headlights.

1700l tub (374gal) - Temp 38C/100F - Heavy Use (2 adults, 3 children), 1hr per day sometimes twice.

ph & TA stable - 7.4, 80 CH - 300+, no ozone

I have been chlorinating with Dichlor...but have a strong feeling I am under dosing (seems scary putting so much in). After a soak on Thursday evening, I checked after 1 hr of getting out FC (0) and TC (3.5). Was told I should have no CC so I needed to shock tub to 10x this difference. So did so with Dichlor 105.2g, left covers off for 1 hr and went to bed. My test kit only goes up to 6.8 for FC, I tested yesterday and its 6.8+ as very pink but we did all go in yesterday, it didn't smell Chloriney and I made us all shower afterwards, just in case. I checked an hour afterwards and it was still above 6.8, left it. Today its still FC 6.8+...is this normal, 36 hours later. Did I put way too much in (I used the calculator)????

So my CYA is now 80, I know high but had no bleach, can this be reduced anyway, other than dumping half of my water? Do I need to worry about this...

I have now purchased Sodium Hypochlorite 14/15% Liquid Chlorine but am pretty shocked that I may need to put in enough bleach to raise the FC to 28ppm each time we use the tub...(basing 2 adults and 3 kids as 4 adults for working out amounts, don't want to over cook it). This would be close to 380ml (10fl oz) of bleach each time we use the tub...this seems crazy to me???? I know it depends on so many things but I need to start some where with how much to put in there????

Thanks in advance
 
Cya that high will interfere with your chlorines ability to sanitize the water. What you describe is exactly why they make non-chlorine shock and ozonators. Since it is a new tub I would suggest you run a purge with Ahhsome as suggested previously, and change the water. Not half the water, all of it. New tubs have been wet-tested at the factory then stored for unknown periods before shipping across the country, and can get some seriously funky stuff growing in the pipes. That may be part of the reason you are using up so much chlorine. It will also help ALOT if everyone is clean before going in, and does not go in and out repeatedly like my kids do.:mad:
Also, bromine is much more forgiving in heavy use conditions, as bromides (think used bromine) are still effective sanitizers, and are converted back to bromine by shocking rather than being burned off like cc. I would also recommend you use a mineral purifier, such as nature2 or spa frog, which interferes with the reproductive cycle of single-celled organisms giving your sanitizer more time to deal with them before they become a biology experiment in your spa.
Read the sticky on bromine, or google it for a ton of info.
 
Thanks for reply. I'm in the UK, and did a drain and purge when I first got the tub. I'm not interested in Bromine at the moment. I get it would be nice for everyone to be clean every time they get in but it's not realistic, so isn't going to happen...I'd really just like the 3 questions in my post to be answered...
 
Ok, fine.
1) No, you did not put too much in. That is what happens when you shock with chlorine.
2) Yes, you do have to worry about locking up your chlorine. It will interfere with it's ability to do it's job. That is also probably why it won't come down now.
3) I don't know.
Best of luck.
 
1. What RDspaguy said
2. What RDspaguy said Go on & dump 1/2 the h20 to reduce cya. It won’t take that long
3. After its full again add enough liquid chlorine to get to 16ppm (shock level for 40cya) & leave it open a while (so cc can off gas) then retest fc & cc if you still have high cc (above 2) without a bather load keep bringing it back to shock level.
You will have to figure out approx how much fc is used each time you use the tub & add the corresponding amount of liquid chlorine. I add a some in advance to prevent ever going too low & then more at exit.
it will definitely be less with just one person vs kids etc.
After use definitely leave the cover off a while 30 min or so it doesn’t trap chloramines
If u wish to avoid so much adding you could always add a swg like the saltron mini.
i have one on a timer - it runs 1 hr 4xs a day - for long double soaks i do add some bleach but it’s usually only a few ounces. Generally though I just turn it back on for an extra hour.
About once every 3 weeks i check my cya & use dichlor instead of bleach to raise fc & cya - your splashout mileage may vary
 
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