Reduce Total Alkalinity Levels

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
Teapot
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Re: Reduce Total Alkalinity Levels

Postby Teapot » Tue 24 Nov, 2020 08:02

Sadly the pool and spa industry do talk a lot of nonsense considering the science. For plaster and tiled pools and spas there is a need to protect the surfaces but not in the case of plastic or vinyl. The 80-120 ta buffer will strongly pull the pH to around 8.1-8.3 but the same industry also sells pH-.
If you have CYA chlorine stabiliser present in the water the pH doesnt matter as much as the correct level of chlorine. PH of 8. Will not hurt your eyes so if that is where your pH is dont bother trying to battle it down.
On indoor pools without CYA pH can be lower.


bobmirror
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Re: Reduce Total Alkalinity Levels

Postby bobmirror » Tue 24 Nov, 2020 11:11

Teapot wrote:If you have CYA chlorine stabiliser present in the water the pH doesnt matter as much as the correct level of chlorine.


That's mad! So actually 'TA buffering' as they describe it, is a complete nonsense then? (i.e. Saying that keeping TA between 80-120 will result in a 'stable' pH value)?

Would you mind explaining some more what you mean in the quoted section I've highlighted above please? (It went over my head a little I think).

I use "stabilised chlorine granules" dichlor
Denniswiseman
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Re: Reduce Total Alkalinity Levels

Postby Denniswiseman » Wed 25 Nov, 2020 02:50

CYA is in Trichlor and Dichlor
Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
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 Calcium Hardness (CH) by at least 7 ppm
To reduce your CYA you have to do a partial drain and refill
Continous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well
bobmirror
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Re: Reduce Total Alkalinity Levels

Postby bobmirror » Wed 25 Nov, 2020 06:56

Denniswiseman wrote:CYA is in Trichlor and Dichlor
Excessive CYA renders your chlorine ineffective and you have to use more to get the same sanitation
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 Calcium Hardness (CH) by at least 7 ppm
To reduce your CYA you have to do a partial drain and refill
Continous use of Trichlor/Dichlor will raise your CYA which means you have to raise your chlorine level as well



Hi Denniswiseman,

Thanks so much for your help. Is there any level of CYA at which a partial drain/refill becomes a necessity for any reason, or can more and more sanitiser just be applied instead? Only I hear of so many hottub users who claim to get 3-4 months out of their water and yet for certain they are using either dichlor or trichlor. (That said, I doubt very much these people are typically testing for CYA... I get the feeling a lot of the hottub community barely pay any actual attention to much other than whether their water looks cloudy or clear!)

Could use of Bromine be an alternative option to combat the issues posed by CYA?

You had also earlier referenced using liquid chlorine (Sodium hypochlorite or plain bleach) and muriatic acid.... whereas currently I use dichlor and dry acid ... are there benefits pros/cons to the former two over the latter two mentioned?

I'm interested to improve my chemical management of the hottub, but there is so much common information about hottub chemistry out there which I struggle to level with either common sense, or the more informed opinions I trust on forums like this one.

Thanks so much again!
Denniswiseman
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Re: Reduce Total Alkalinity Levels

Postby Denniswiseman » Wed 25 Nov, 2020 08:38

This post of Chlorine / CYA Chart indicates what sanitation is required for varying levels of CYA
Sodium Hypochlorite doesn't contain CYA only salt which isn't a problem. Only problem it doesn't store for long periods and the strength diminishes
For the amount you use dry acid would probably be fine
I don't have knowledge of Bromine however it works better in higher temperature but is slower in sanitising
Whereas chlorine is fast acting and readily availabe (bleach)
Teapot
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Re: Reduce Total Alkalinity Levels

Postby Teapot » Thu 26 Nov, 2020 07:51

bobmirror wrote:
Teapot wrote:If you have CYA chlorine stabiliser present in the water the pH doesnt matter as much as the correct level of chlorine.


That's mad! So actually 'TA buffering' as they describe it, is a complete nonsense then? (i.e. Saying that keeping TA between 80-120 will result in a 'stable' pH value)?

Would you mind explaining some more what you mean in the quoted section I've highlighted above please? (It went over my head a little I think).

I use "stabilised chlorine granules" dichlor

All carbonates form a buffer to prevent pH change. The issue from a pool perspective is that this buffer is around pH 8.1-8.3. So the industry tells everyone to keep spending money to get this down to a pH of 7.2-7.6.
This reduces the TA which then means adding bicarbonate of soda to increase the TA which then causes pH to rise and so it goes on.

With. TA of 50ppm there is still about 7 times more carbonates in the water than the air so as nature tries to get to equilibrium the carbonates escape the water causing a pH rise. The more carbonates (TA) the quicker the pH rise with aeration and temperature. Also the higher the TA the stronger the buffer pull is to pH 8.1-8.3 so the more acid is required to get the pH to move.
I have a customer who's supply water is TA 27ppm, when I first met him I panicked because I was trained by the industry to get that figure to at least 80ppm or the world would surely end. Only his pH was stable and if anything would fall slightly with the addition of trichlor tabs. Switching to bleach stopped this fall and he never bought pH minus again. The water was fantastically clear ( I changed the filter media to Drydens AFM).
I then brought my own TA down to 40ppm hard to get it lower, but as stated earlier I haven't added pH minus in 2 years, actually it could be longer than that.
In a report which I will find they tested the sanitiser levels at various pH levels and when CYA is present there was negligible difference un sanitiser power right the way up to pH 8.8-9.0 the most important requirement was to have sufficient chlorine to provide a free unbound chlorine level sufficient to sanitise. Thus battling with pH is now a thing of the past. Give the industry 20 years and they may get the message.
Teapot
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Re: Reduce Total Alkalinity Levels

Postby Teapot » Thu 26 Nov, 2020 08:13

bobmirror wrote:

Could use of Bromine be an alternative option to combat the issues posed by CYA?

Not saying you can't use bromine but:
Bromine cant be protected from sunlight degradation.
Bromine smells nasty of stagnant water.
Bromine is more toxic/carcinogenic to humans than chlorine and in a spa/hot tub your nose is just above the waterline where the chemical concentration is highest.
By contrast CYA is easy to manage and a little bit of bleach easy to administer.

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