Using trichlor tabs to increase CYA

[wysocki]

I had a huge cya problem (110) with my pool so I drained it, replaced the water, and while I was at it, installed a SWG. Life is good!!!

BUT! Now I actually have cya a little low (60) and I really hate to add stabilizer (like an ex-alcoholic avoiding a beer). I'm thinking that, for the winter, I could turn off my SWG (which devours my acid) and just use some trichlor tabs to maintain a low chlorine presence, at the same time adding some cya!

Good idea? If so, I need to know how many ounces of cya are in a tab. Poolmath tells me I need 32oz of Stabilizer to get from 60 to 70, so I want to know how many tabs that equates to.

 

[mknauss]

The SWCG has no effect on your need for lowering the pH with acid.

No need to raise the CYA at this time of year either.

 

[wysocki]

Really? Since I put the salt pool in, I have been using about 1/2+ gallon a week in acid. Almost never had to use any before that. My friends with salt pools say the same thing.

Good to know I don't need to increase cya now. But come summer, I'd like to know the exact effect of tabs on it.

 

[mknauss]

The process of creating chlorine with a SWCG is pH neutral. Are you comparing it to using trichlor in the past?

 

[Rancho Cost-a-Lotta]

I'd like to know the exact effect of tabs on it.

Use the "Effects of Adding" function in Pool Math. Each tablet contains 8 oz. of trichlor.

 

[wysocki]

In the past, I've varied between trichlor tabs and liquid chlorine. Always had chlorine at the bottom of the scale since it bothered the wife. Rarely had to use acid. Here's my current readings:
FC: 3.5
PH: 8.6
TA: 60
CH:375
CYA: 60

I've seen several articles on TFP that refer to increased use of acid with SWG. Have my Hayward SWG set at 10% now. Don't know why, but my PH goes up about .1 per day.

@rancho: "Each tablet contains 8 oz. of trichlor." But how much CYA?

 

[mknauss]

How did you measure a pH of 8.6?

 

[wysocki]

With my K-1000 kit and ATC electronic tester.

 

[Rancho Cost-a-Lotta]

@rancho: "Each tablet contains 8 oz. of trichlor." But how much CYA?

Trichlor is chlorine bound by cyanuric acid. Under chemical additions, use "trichlor, 8 ounces" and effects will show below. Here's a screenshot...

 

[mknauss]

With my K-1000 kit and ATC electronic tester.

It is chemically very difficult to have a TA of 60 with a CYA of 60 and a pH of 8.6 unless caustic as been added to the pool.

Have you calibrated the pH pen? The K1000 will not show above 8.2 ppm.

 

[wysocki]

You're right, it really did need calibration! My Taylor K1000 was off the scale so I assumed the pen was right. Anyway, I've now calibrated the pen and added baking soda and acid over the weekend and now I'm here:
FC: 3.5
pH: 7.4
TA: 70
CH: 375
CYA: 60

How's that look?
And I still say that my new swg takes a lot of acid. Here's a quote from taylortechnologies.com website: "a byproduct of the salt to chlorine reaction is sodium hydroxide (NaOH). The production of sodium hydroxide will push the pH higher, requiring more frequent addition of acid in salt pools.".

 

[mknauss]

The creation of chlorine in a SWCG is essentially pH neutral. Many members never add acid to their SWCG pools. Fill water with elevated TA and aeration cause pH to rise.

 

[Donldson]

added baking soda and acid over the weekend

This will be an endless loop. If your pH is constantly rising then you need to let your TA drop more. You're used to managing a pool with a steady diet of highly acidic pucks, that required a high TA to compensate. Now that you're using a more neutral source of chlorine you need a lower TA to keep the water stable.

It's not the SWG causing the need for acid, your water (at the levels you kept it at) has always needed that supply of acid and you took that away when you installed the SWG.

 

[wysocki]

The creation of chlorine in a SWCG is essentially pH neutral.

But as Taylor points out, it's a byproduct of that reaction that raises ph. Or it must be birds droppings that are hitting my ph then!
My fill water is pH: 8.0 TA: 80 CH: 100 but I rarely use it, especially in cool weather. And no aeration or waterfall.

 

[Brad_C]

My fill water TA is 110. If my TA is > 70 the ph always drifts up. If I get it below 70 then I generally don't have to add acid. Last year I think I added acid twice in 12 months and the ph settled nicely around 7.8.

I get a lot of washout over winter, so the TA starts the summer low and creeps up with water replacement over summer. A few years ago I dropped it to ~40 (lots of acid and aeration) and didn't have to touch the ph for the whole year.