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Author Topic: Bleach vs Dichlor  (Read 6714 times)

av8r

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Bleach vs Dichlor
« on: November 28, 2015, 01:48:03 pm »
My CYA is 151.  Around 110 I started using 6% bleach (ya, I now know too late) but the CYA has continued to climb to 151 today as measured by dealer's ALEX system.  The person doing the test at the dealer suggested liquid chlorine or bleach burns off faster than granules.  I don't recall reading that here or elsewhere so can anyone confirm if this is true?

At 151 CYA I guess it's time to do at least a partial water change.  If I stopped using Dichlor and only used bleach will CYA ever drop or will the level remain constant?

Thanks

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Bleach vs Dichlor
« on: November 28, 2015, 01:48:03 pm »

Hottubguy

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Re: Bleach vs Dichlor
« Reply #1 on: November 28, 2015, 02:21:06 pm »
Cya only comes down with dilution. It shouldn't have climbed after you stopped using dichlor. I wonder if Alex was a little off on his readings

av8r

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Re: Bleach vs Dichlor
« Reply #2 on: November 28, 2015, 02:28:10 pm »
Cya only comes down with dilution. It shouldn't have climbed after you stopped using dichlor. I wonder if Alex was a little off on his readings

I've only been using bleach a short time so I may have unintentionally mislead on that point.

What is considered to be the point at which CYA is too high and the water needs to be replaced?
« Last Edit: November 28, 2015, 02:30:45 pm by av8r »

Hottubguy

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Re: Bleach vs Dichlor
« Reply #3 on: November 28, 2015, 03:41:54 pm »
Cya only comes down with dilution. It shouldn't have climbed after you stopped using dichlor. I wonder if Alex was a little off on his readings

I've only been using bleach a short time so I may have unintentionally mislead on that point.

What is considered to be the point at which CYA is too high and the water needs to be replaced?

I would defer to Chem Geeks opinion on that but my rule of thumb has always been 100.

Vinny

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Re: Bleach vs Dichlor
« Reply #4 on: November 29, 2015, 03:22:39 pm »
Chem geek is a great proponent of dichlor then bleach method. Chlorine does become less effective as the CYA increases and in a hot tub it can increase rather rapidly. Using bleach in a hot tub is a fairly newish concept that came from using it in the pool. I was around here when chem geek started posting here and he got a lot of flack about using bleach in a hot tub. There was another poster who came around the same time that was more "in your face" about using bleach but chem geek truly understands this stuff IMO and is able to explain it for those of us who may not.

People do (did) use just dichlor in the tub for many years without problems. I did go 3-4 months using dichlor exclusively without a problem. The rule of thimb that I use is switch to bleach when you get to 30 or so PPM CYA. Should you worry about it if it's 8 below and you can't do anything about it - IMO, nope. If it's a nice day and you can do a partial of full drain and refill - yeah go ahead. And you can start using bleach anytime after reaching that 30 PPM CYA level.

The one thing that chem geek mentions is about borates and the use of bleach;this is one concept that he has explained and quite honestly I don't get. But I also see that everybody's water does react differently for whatever reasons. I have added bleach to my tub and I don't get pH swings as is mentioned; I sometimes do use borax so that may be why. But I also add baking soda and have my pH rise and lock in for weeks as well; it acts differently then what other people's water acts like.

chem geek

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Re: Bleach vs Dichlor
« Reply #5 on: November 29, 2015, 09:58:42 pm »
My CYA is 151.  Around 110 I started using 6% bleach (ya, I now know too late) but the CYA has continued to climb to 151 today as measured by dealer's ALEX system.  The person doing the test at the dealer suggested liquid chlorine or bleach burns off faster than granules.  I don't recall reading that here or elsewhere so can anyone confirm if this is true?

At 151 CYA I guess it's time to do at least a partial water change.  If I stopped using Dichlor and only used bleach will CYA ever drop or will the level remain constant?

It is complete and total B.S. that chlorinating liquid or bleach "burns off faster than granules".  Once ANY source of chlorine dissolves in the water it produces EXACTLY the same type of chlorine -- the only difference is what ELSE the type of chlorine adds.  The following are chemical facts that are independent of concentration of product or of spa (or pool) size.

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Cal-Hypo by at least 7 ppm.
For ANY type of chlorine, for every 10 ppm FC the chorine when used/consumed will become 8 ppm salt.  When using most hypochlorite sources of chlorine (e.g. chlorinating liquid, bleach, lithium hypochlorite), there is an additional 8 ppm salt added upon addition.

What the dealer may be referring to is if you were to use ONLY bleach with no CYA in the water at all.  In that case, the active chlorine level is far too strong and it will outgas faster and react faster so get used up more quickly.  However, that's not the proper way to use bleach.  One should initially add or build up CYA to the water which one can do either by adding pure CYA initially or more easily can just use Dichlor for a while until the CYA builds up.  Then switch to using bleach.  About once a month, use Dichlor for a day to build CYA back up since it slowly gets oxidized by chlorine at a rate of roughly 5 ppm per month in spas.

So if you stopped using Dichlor your CYA will SLOWLY drop, but for practical purposes it won't drop fast enough.  As for when CYA becomes a problem, technically you can just raise your FC target proportionally for the same active chlorine level.  3 ppm FC with 30 ppm CYA has the same active chlorine as 10 ppm FC with 100 ppm CYA or 20 ppm FC with 200 ppm CYA.  However, most people don't want to start their soak with a high FC level -- not because the chlorine is too active (because it's not), but because they want to avoid the smell of chloramines that will result from the chlorine reacting with ammonia and other chemicals (such as urea) in your sweat and urine.  Usually people add a large amount of chlorine AFTER their soak in a quantity sufficient to oxidize their bather waste and still have a 1-2 ppm FC residual 24 hours later for their next soak (if they soak every day).

As for whether 151 ppm CYA is too high, it's not so bad as to when rates of hot tub itch/rash/lung seemed to be more prevalent which was at around 200 ppm or higher (though there was one incident between 100 and 200 ppm CYA) and it's also not as high as when a water change is typically needed due to the water getting more dull which is roughly at 250 ppm CYA (i.e. after 272 ppm FC has been cumulatively added from Dichlor).  So up to you as to whether you want to do, say, a half drain/refill to get to around 75 ppm CYA which is certainly reasonable (the 30-40 ppm CYA target is to have a somewhat higher active chlorine level for reasonably fast oxidation of bather waste while not being too high).

av8r

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Re: Bleach vs Dichlor
« Reply #6 on: November 29, 2015, 10:07:16 pm »
Thanks to all for the information.  Since this is our first tub and I'm learning as I go, I'm going to hold off on the drain, partial or otherwise, for now.  Water looks the same as it has, no unusual smells, no one is complaining of any issues while or after soaking.  My plan was to run Ah-some, then drain, flush, etc around the second week of December which I hoped would get me through February before I'd have to change the water again. 

Best laid plans and all that.  :)

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Re: Bleach vs Dichlor
« Reply #6 on: November 29, 2015, 10:07:16 pm »

 

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