Chlorine types and CYA

Chlorinating, maintaining the right chlorine levels,
chlorine problems. Dichlor, trichlor, cal hypo, bleach,
granules, chlorine pucks and chlorine sticks.
btanchors
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Chlorine types and CYA

Postby btanchors » Sun 12 May, 2024 14:42

Greetings,

I have been using Trichlor tablets (Typically about 2-3 tablets in a floater keeps me at about 3ppm for my Chlorine level) to maintain my chlorine levels. But I have noticed my CYA levels slowly creeping up. This morning, I went to Leslie's Pool to have my water analyzed. Free Chlorine was at 2.36, but CYA Is now at 78. I told the person at the counter I was thinking of switching to liquid chlorine (i.e., unstabilized) chlorine so that my CYA levels would no longer go up.

The person said No - and suggested this instead:

Use only one 3 inch tab at a time. Then, shock the pool with Hypochlorite, which is unstablized Chlorine, once a week. They said the increase in Chlorine from the Shock would last almost a week, when it would be time to shock it again. When CYA Levels become excessive, place a sump pump on the top step of the pool, and pump out water until the level goes down about two inches. She said CYA tends to concentrate in the top levels of the water, so pumping out about the top two inches should reduce CYA levels by about 40 points. Placing the sump pump on the top step means it would pump out predominantly the top layer of water where the CYA tends to be concentrated.

She also said using only one 3 inch tab per week would add only about 1 point to the CYA level each week.

I heard that if I switched to liquid chlorine, I would have to add the chlorine every one-two days, so I must admit, I think I like the leslie's idea better. But I would like to confirm the leslie's approach is valid. Can some of you experts out there chime in? Is the above approach reasonable?

My pool is 15,000 gallons, pebble finish. Not salt water - regular chlorinated water. It has an attached heated Spa. i have cartridge filters.


Teapot1
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Re: Chlorine types and CYA

Postby Teapot1 » Mon 13 May, 2024 01:17

Oh dear, do Leslies just make up this nonsense on the spot or do they have a training school called BS High?
Water soluble chemicals stay mixed throughout the water, there is no high concentration point top or bottom. In theory over winter with completely undisturbed water you might get a tiny bit higher concentration of CYA at the deepest part of the pool because CYA is denser than water.
So drain some water from any point. Dont carry out the Leslie's silly idea it will only lead more sales for them and during the week low chlorine invites issues and weekly shocking is not really shocking which is a sustained high level until you kill and oxidise everything from the water.
If you are unable to add a jug of bleach every day or two maybe invest in a chlorine dosing pump or at the very least a perastaltic washing liquid pump and a digital timer to dose daily.
Continuing to use chlorine pucks will just continue to raise the CYA which means cost for replacing water that you have treated and possibly heated. Then there is the time and attention required to carry out the draining and topping up.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
btanchors
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Re: Chlorine types and CYA

Postby btanchors » Mon 13 May, 2024 14:14

Teapot - thank you very much for your response! So it sounds like I am back to my original idea of using liquid chlorine, which does not contain stabilizer.

My question now is, how much do I need to add, and how often do I need to add it? My pool is 15,000 gallons and the liquid chlorine I would use is 10 - 12.5% Concentration from Leslie's.
Teapot1
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Re: Chlorine types and CYA

Postby Teapot1 » Tue 14 May, 2024 00:22

To make life easy for yourself, I would use the pool calculator or one of the apps now available.
https://www.troublefreepool.com/calc.html
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
btanchors
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Re: Chlorine types and CYA

Postby btanchors » Wed 15 May, 2024 12:20

Teapot1 - I looked and played with the calculator. It tells me how much liquid chlorine to add, but it does not tell me how often it needs to be added to maintain at a given level. Can you or anyone tell me how often I need to add liquid chlorine to maintain a given level, assuming the information above?
Teapot1
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Re: Chlorine types and CYA

Postby Teapot1 » Wed 15 May, 2024 13:22

Chlorine gets used up disinfecting the water and its impossible to say. The cleaner the water the longer it lasts nut the sun will still degrade the chlorine. If you regularly test the water you'll soon see and work it out. If you suddenly see it being used quickly more than usual then shocking may be whats needed.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
Teapot1
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Re: Chlorine types and CYA

Postby Teapot1 » Thu 16 May, 2024 17:29

They are calcium hypochlorite, that will add calcium to the water and that can lead to scale build up and clouding of the pool water. They wont of course raise CYA as they dont contain any. Best used in a feeder rather than a skimmer as they turn to mush. Also and this is very important, never mix cal hypo with sodium hypo (trichlor or dichlor) tabs as the mixture can explode. It is ok once they are fully disolved into the water of the pool.
Depending on how hard your water is to start with this may or may not be a good idea. You may also want to lower your alkalinity as calcium hypochlorite will raise both the pH and the alkalinty and calcium level as previously stated.
I may not give you the answer you want to hear, but I will give an honest opinion of your situation as you decribe it.
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Re: Chlorine types and CYA

Postby MSpitz » Fri 17 May, 2024 06:26

BT,
For years, I had a huge problem with extremely high CYA and tried everything. The only way I was able to control it was using liquid chlorine for regular chlorination and tablets very (few) times (needed them while away). After using few tablets, CYA would rise but not significantly.

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