Chlorine tablet chemistry

New2PoolsInAZ

Member
Jul 13, 2019
16
Sun City, AZ
I live in sunny hot Phoenix and this is my first year with a pool, it was finished in May. I use Trichlor to chlorinate it and when I did my first CYA test a couple of months ago it was over 100. I diluted the water for over 24 hours (filling and draining at the same time) bringing it to 50. I recall also then lifting CH at that time to 250. Today (2 months later after the hotest part of the Phoenix summer) the pool hit CYA of about 170 and CH at 375. Wow, had to dilute again this time for about 36 hours. And I am going to start using Bleach now to chlorinate, something I tried doing 2 months ago but thought it was not worth it. I was wrong.

I am hoping to ask here, to someone who knows chemistry, why they cannot make a tablet that does not contain tons of CYA? The alternative seem to be ones that contain calcium but adding cacium in Phoenix wher where the water is hard and there is much evaporation is not much better. Or lithium which is very expensive and not readily available. Clearly there would be a huge market for a tablet that did not add anything to your pool but sodium hypochlorite. And further, why even add CYA to Trichlor? You can put in your own CYA in the pool just once and leave it. To someone with as little knowledge of this as me, Trichlor minus CYA equals a huge selling product.

I am aware there are simple answers to these questions... Just want to know what those are. Thanks!
 

beautifulpool

Silver Supporter
Jun 2, 2019
132
North TX
I live in sunny hot Phoenix and this is my first year with a pool, it was finished in May. I use Trichlor to chlorinate it and when I did my first CYA test a couple of months ago it was over 100. I diluted the water for over 24 hours (filling and draining at the same time) bringing it to 50. I recall also then lifting CH at that time to 250. Today (2 months later after the hotest part of the Phoenix summer) the pool hit CYA of about 170 and CH at 375. Wow, had to dilute again this time for about 36 hours. And I am going to start using Bleach now to chlorinate, something I tried doing 2 months ago but thought it was not worth it. I was wrong.

I am hoping to ask here, to someone who knows chemistry, why they cannot make a tablet that does not contain tons of CYA? The alternative seem to be ones that contain calcium but adding cacium in Phoenix wher where the water is hard and there is much evaporation is not much better. Or lithium which is very expensive and not readily available. Clearly there would be a huge market for a tablet that did not add anything to your pool but sodium hypochlorite. And further, why even add CYA to Trichlor? You can put in your own CYA in the pool just once and leave it. To someone with as little knowledge of this as me, Trichlor minus CYA equals a huge selling product.

I am aware there are simple answers to these questions... Just want to know what those are. Thanks!
Hi New2poolsinAZ
My best guess, is that while cya may be “the pool guy’s” best friend (maintaining over 100 pools per week) who has neither neither time nor inclination to go to each clients home daily, and those in the retail business who make ?millions selling stabilized chlorine may love it, customers who do their own pool care learn cya over a very small amount, is not our friend
But because we think adding Acid (which our pool used to get automatically as it was Already in the Di-Chlor or tri-chlor - chemistry equation, but once we see the light - and rightly “swear off” over stabilizing our pools-then a few months or a year goes by- and we think just because we now need to add acid, that something is wrong. In reality nothing is wrong.
But if we don’t know that, then we “wrongly swear off LC
AND run back to the pucks! ?‍♀
Yep, I got more than 1 t-shirt on that dance ...
 

New2PoolsInAZ

Member
Jul 13, 2019
16
Sun City, AZ
Nice :) I imagine so many people would buy the equivelent of Trichlor without CYA. I am just wondering if there is something in the manufacturing process that requires them adding CYA, else I would imagine they would have an alternative product for those who do not want to add it.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
19,302
Northern NJ
I am hoping to ask here, to someone who knows chemistry, why they cannot make a tablet that does not contain tons of CYA?
Chlorine is a gas, not a solid. To chemically have chlorine you can carry you need to bind chlorine to something.

That can be CYA, calcium or lithium that create the type of pucks sold that contain chlorine bound to solids.

Or chlorine can be bound to water and salt in the form of liquid chlorine or bleach.

Commercial pools use chlorine gas injection systems so they can use chlorine without introducing other chemicals to the pool. Those systems are impractical for residential use.

Simple enough?
 
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Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,563
NW Ohio
They don't add CYA. The chemical is trichloroisocyanuric acid, which means it is CYA with chlorine added. Why? Because chlorine is a gas and must be bound to something because the only way to create pure solid chlorine is to freeze it down to -150 F or pressurize it far more than humans can withstand. Neither of these are situations are very conducive to a swimming environment. So to make chlorine a solid it must be bound to a solid. And the thing about dissolved solids is that they don't evaporate. So whatever the chlorine is bound to will build up indefinitely. Trichlor is the easiest to compress in to a puck of the options.

It's CYA, calcium, or lithium. Lithium is in much higher demand for other things so don't expect that to ever make a comeback. That leaves calcium or cyanuric acid, or liquid, or make your own (SWG).
 

Jimrahbe

Mod Squad
TFP Expert
LifeTime Supporter
Jul 7, 2014
18,740
Bedford, TX
John,

My Chlorine comes without any CYA or Calcium.. In fact I have to actually add CYA... I am of course talking about a saltwater pool..

Many people in AZ have saltwater pools and they work great. A Saltwater Chlorine Generator (SWCG) converts the salt into chlorine without any binders..

Thanks,

Jim R.
 

beautifulpool

Silver Supporter
Jun 2, 2019
132
North TX
Chlorine is a gas, not a solid. To chemically have chlorine you can carry you need to bind chlorine to something.

That can be CYA, calcium or lithium that create the type of pucks sold that contain chlorine bound to solids.

Or chlorine can be bound to water and salt in the form of liquid chlorine or bleach.

Commercial pools use chlorine gas injection systems so they can use chlorine without introducing other chemicals to the pool. Those systems are impractical for residential use.

Simple enough?
in the late ‘70’s, The huge Air Force pool we lifeguarded at, had a room with a gigantic tank with hoses and Meters ... some form of chlorine I thought ...
But fast forward to today, our choices are cya? calcium ? or salt? in the pool after the chlorine leaves? For SWG, those folks must “start” with salt. Since I don’t have a SWG, i “end up” with a little salt.... does that show up in my TDS #? ... Im wondering if calcium left behind in the pool water after using calcium hypochlorite shows up in the TDS# also?....as Salt does when one uses sodium hypochlorite??
 

Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,563
NW Ohio
in the late ‘70’s, The huge Air Force pool we lifeguarded at, had a room with a gigantic tank with hoses and Meters ... some form of chlorine I thought ...
Yes, that was likely gaseous chlorine. Not available on the consumer market for reasons I hope I don't have to explain. And for the record it did add salt to the pool, as the reaction consuming chlorine reduces it to chloride.
 
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beautifulpool

Silver Supporter
Jun 2, 2019
132
North TX
TDS is a reading of all Dissolved Solids in your water. Salt, CYA, calcium, magnesium, potassium, etc.
Since my TF-100 gives CH of 275, and we then Can plug our other chemistry numbers in to get a saturation score - ya know how TDS is subtracted (not the actual TDS number per say-rather a factor -like i think around 12.1 or close to for TDS under 1000) - and so my factor would be 12.1 since my TDS are under 1000ppm )
Anyway what CONFUSES me is this- since a factor for calcium hardness is assigned and that factor is added to the actual pH, and a factor is assigned for TA(minus cya adjustment) and a factor is assigned for water Temp, and these factors are added to the actual pH # for one side of the equation.
Then on the other side-TDS -not the actual TDS # number -but the assigned factor for the TDS # .....is subtracted.
Am I the only person this bothers? Cause it seems like we are factoring in some of the TA and CH on both sides of the saturation equation .....
 

beautifulpool

Silver Supporter
Jun 2, 2019
132
North TX
Yes, that was likely gaseous chlorine. Not available on the consumer market for reasons I hope I don't have to explain. And for the record it did add salt to the pool, as the reaction consuming chlorine reduces it to chloride.
I was a teenager at the time and it’s a good thing they had me lifeguarding only! ;)