Trichlor and Liquid Chlorine experiment!?

[Ourad]

So we are saying cya does actually degrade in some situations? because I thought I was taught in pool school that only water removal drops it?? I might give this a go if so, it’s 90+ here and adding a gallon of bleach every other day gets old, but I was afraid of the cya buildup.

 

[mknauss]

Testing will tell you. In high UV areas with elevated water temperatures, you will see some degradation of CYA levels. However, pucks will never add the 2-4 ppm of FC you need each day and thus adding liquid chlorine every day during the summer is still necessary.

 

[ajw22]

How_is_CYA_Lost_and_Degrade_in_Pool_Water?

 

[DanF]

Trichlor for the win?

LOL. I think the moral of the story, at least in the SW deserts, is that they can certainly co-exist if needed. The actual balance/ratio between the two can be up to the individual. If trichlor is used, more frequent CYA testing would be required, at a minimum to ensure that the trichlor is offsetting the CYA degradation here. Another benefit of trichlor, although small, is that it lessens the amount of MA I need, as it keeps pH down a bit.

 

[mknauss]

If we leave in the summer for a while, I float a dispenser of trichlor in the pool. Primarily for the acid. The SWCG generates all the chlorine I need.

 

[Oly]

Someone needs to do a study on the degradation rate of trichlor pucks relative to water temps and dispenser placement or with an in line tab chlorinator attachment.
Trichlor tabs are unique in that they do provide FC over time, they lower pH and also add CYA. They can be used to cover for days when away, assuming of course you have room to raise your CYA slightly and will not drive your pH too low.
I know that pucks will dissolve faster in warmer water. I imagine they dissolve faster in an inline chlorinator device or if a floater is positioned in front of a return jet. Also run time per day would be a factor.
I seems if you could graph the degredation rate that represents your system you could then roughly estimate how many tabs it would require to maintain your daily FC demand and also anticipate the pH effects and CYA additions of those tabs over time. Now I would expect there would be a rate curve as the days progressed and the tabs become smaller.
Of course the effect of the tabs would be significantly diminished after what, 4 to 5 days. Eventually they would completely dissolve so probably not adequate for a vacation of more than 4-5 days right?
Anybody want to step up and do some research?

 

[duraleigh]

Or you could test CYA monthly and make a one time dose if your CYA has degraded.

 

[AndyTN]

I use trichlor pucks all year as supplemental FC to dosing with bleach. I have always noticed that the CYA the PoolMath app says should accumulate over the summer is never even close. I normally start out each spring with CYA of 20 or 30 and the trichlor pucks give me free CYA over time but I have never had it rise to more than 60. According to PoolMath, my CYA should be close to 100 by the end of the summer based on going through 18-20 lbs of trichlor. This is even accounting for a small drop in CYA from splashing and back washing.

I keep my rainbow feeder on setting 1 out of 5 and will add bleach every 2-3 days after testing to keep precise FC in check. This usually yields a 50/50 mix of trichlor and 10% bleach averaged over the summer. I never have to use MA since the trichlor lowers the ph slightly and I would much rather add a little baking soda than deal with MA. For all the people currently complaining of bleach shortages due to the pandemic, no one is going out to buy trichlor to make sanitizer. The cost per ppm of FC from trichlor is cheaper than from bleach as well.

Should someone switch to 100% trichlor and never test their CYA? Absolutely not but if your pool already has a feeder for the pucks and you live in a warm climate, why not utilize the benefits of trichlor? I have thought about installing a stenner pump for the convenience factor but I can't justify the money/effort when I can just use the existing trichlor feeder.

 

[Katodude]

Sounds like you have a very workable plan. I have a SWG which works great. However, this time of year with the rain and the constant exposure to sun I like to run FC a little hot and lose a lot of CYA. So like you I supplement with pucks which is very helpful.

However, these plans are based on experienced use and very frequent testing. Generally not recommend for a newcomer to TFP methods.

 

[Dtkokay]

This thread hits home with me because I live in Texas and have a bunch of leftover trichlor tablets that I don’t use. If my CYA does naturally burn off from the intense Texas sun, I was planning to use the tablets to boost up the CYA when needed.

My pool is less than 3 months old, so I’m still learning its water characteristics.

 

[mariane]

I use trichlor pucks all year as supplemental FC to dosing with bleach . . . . . . . . I normally start out each spring with CYA of 20 or 30 and the trichlor pucks give me free CYA over time but I have never had it rise to more than 60. According to PoolMath, my CYA should be close to 100 by the end of the summer based on going through 18-20 lbs of trichlor. . . . .
. . . . . . and will add bleach every 2-3 days after testing to keep precise FC in check. This usually yields a 50/50 mix of trichlor and 10% bleach averaged over the summer. . . . . . . . no one is going out to buy trichlor to make sanitizer. The cost per ppm of FC from trichlor is cheaper than from bleach as well.

This is a very interesting discussion and different perspective on trichlor.
I'm wondering how so many pools end up with CYA through the roof, if this is the case. We dump water every fall and refill every spring because of our hard freeze during the winter. I have noticed the CYA is ~ 20 in the spring but that is after refill.
So cost per ppm of FC from trichlor is cheaper than bleach (10 or 12.5%)? Is there a comparison numbers chart to look at?

 

[Dtkokay]

This is a very interesting discussion and different perspective on trichlor.
I'm wondering how so many pools end up with CYA through the roof, if this is the case. We dump water every fall and refill every spring because of our hard freeze during the winter. I have noticed the CYA is ~ 20 in the spring but that is after refill.
So cost per ppm of FC from trichlor is cheaper than bleach (10 or 12.5%)? Is there a comparison numbers chart to look at?

I think it’s too hard to have a reliable comparison chart because it depends on how much you pay for trichlor and liquid chlorine. Those costs are highly variable. For me, trichlor costs $0.48 / ppm of chlorine (based on buying 35 lbs for $76 at Home Depot), and liquid chlorine costs $0.71 / ppm (based on $3 / gallon of 10% at Home Depot). Liquid chlorine is around 50% more expensive for me than trichlor.

 

[mknauss]

Be sure you are accounting that only about 2/3rd of trichlor is chlorine.

 

[mariane]

In my search, I could not find on the MSDS how much chlorine was actually in each tablet.

 

[Dtkokay]

Be sure you are accounting that only about 2/3rd of trichlor is chlorine.

I used the Pool Math "effects of adding" calculator. For my size pool, it says 1 lb of trichlor adds 4.6 ppm of FC, and 1 gallon of 10% bleach adds 4.2 ppm chlorine. I then used the prices I pay for this stuff to come up with a $ / ppm.

 

[DanF]

I think it’s too hard to have a reliable comparison chart because it depends on how much you pay for trichlor and liquid chlorine. Those costs are highly variable. For me, trichlor costs $0.48 / ppm of chlorine (based on buying 35 lbs for $76 at Home Depot), and liquid chlorine costs $0.71 / ppm (based on $3 / gallon of 10% at Home Depot). Liquid chlorine is around 50% more expensive for me than trichlor.

Be sure you are accounting that only about 2/3rd of trichlor is chlorine.

Good points above. As an alternative to having to know the chemical composition of trichlor, I went to PoolMath for @Dtkokay's pool.
35 lbs of trichlor would raise generate 154 ppm in a 25K gallon pool. Cost is $76.
It would take 38.5 gallons of 10% bleach to generate 154 ppm. That cost would be $116.
35 pounds of trichlor will also generate 93 ppm of CYA, and lower pH by 8.2, so some conditioner and muriatic acid savings would accrue from using trichlor.
Of course you'd need a lot of R-0013 to test your CYA to ensure you kept in range! And with a tri-chlor only approach more frequent draining as well.

 

[DanF]

I used the Pool Math "effects of adding" calculator. For my size pool, it says 1 lb of trichlor adds 4.6 ppm of FC, and 1 gallon of 10% bleach adds 4.2 ppm chlorine. I then used the prices I pay for this stuff to come up with a $ / ppm.

Beat me to it!

 

[mknauss]

With trichlor only, it is very difficult to impossible to maintain your FC in the target range of the FC/CYA Levels.

Also be sure you only get plain trichlor tablets. You do not want to add copper to your pool.

 

[DanF]

With trichlor only, it is very difficult to impossible to maintain your FC in the target range of the FC/CYA Levels.

Exactly - that's because the 154 ppm of FC in my example above would last (at 3 FC/day) no more than 51 days; likely a lot less because of the high CYA. But the 93 ppm CYA would be there for a long time.

Another downside of tabs is that I really don't know when I'm getting that 4.4 ppm FC/tab, because of varying dissolution rates. With LC I know it will be there within the hour.

 

[AndyTN]

With trichlor only, it is very difficult to impossible to maintain your FC in the target range of the FC/CYA Levels.

Agree here with this statement. I haven't used 100% trichlor since my first year owning a pool when I was following pool store methods, prior to me finding TFP. I was doing full blast trichlor with the weekly bag of powdered "shock" (cal hypo) and I wasn't even testing for CYA then. I am shocked I didn't have any problems that year.

This is why I am stating I use approx 50/50 of 10% bleach and trichlor. The trichlor is continuously supplementing small amounts of FC in addition to my more precise bleach doses after testing.

Also, if the summer heat and UV rays degrade the CYA as discussed here, someone in Michigan is going to have a different CYA experience than in the hot South or AZ.