Finally got my CYA under control and do NOT want to have to go through that again. Questions.

[Kat-A-Tonic]

So I did a partial drain and refill to get my CYA under control. At the time, my test kit had not arrived, but Leslies test showed it at 160. I drained 3/4 of the pool and talked my neighbor into allowing me to use his hose to fill my pool as I am on a shared well, and the others would hate me if I ran it dry. Took a sample to Leslies after the drain and they showed 38 ppm for the CYA and I thought awesome, I love it when a plan comes together. Fast forward a few days, and the test kit arrives. Just for giggles I run the CYA test and it seems to be over 100. I think I must have goofed up the test, so I run it again. Same result. Run the diluted version and get 55, confirming the over 100 result. Not sure what happened, but my CYA must have been at least 350 to 400 before the drain and fill. Not sure how I never had issues with algae. Anyway, I talked the neighbor into using his hose again and now I am testing out at between 30 and 40. I am using bleach so I do not expect any increase in CYA unless I want to use pucks for a vacation, or if I decide to add some CYA since I am in Mesa AZ and the sun is slightly strong here.

So my question is how much CYA is in the tabs, and does CYA ever dissipate on its own over time. I think I want to raise it to at least 40. I also plan on using pool water to clean my cartridges and then replace that water with softened water from my home system, since the well water is fairly hard. I realize that that will slightly lower the CYA every time I do it, leaving room to use a few tabs on occasion.

All chemistry is good now except the TA is 130 and I am taking steps to lower it with acid and aeration.

 

[ajw22]

So my question is how much CYA is in the tabs,

An 8 oz trichlor tablet in your 17,250 gallon pool will raise FC by 3.2, CYA by 1.9 , lower pH by 0.17, and add 2.6 ppm of salt.

and does CYA ever dissipate on its own over time.

Sort of. Read...

CYA - Further Reading

www.troublefreepool.com

 

[Mdragger88]

PoolMath effects of adding can tell you all the effects of each chemical you intend to add.
Most 3” pucks are 8oz - check your packaging though as there are jumbos as well as 1”.

 

[Kat-A-Tonic]

Thanks for the info. At almost 2.0 ppm per tab CYA increase, I can see why mine might well have been almost 400. Why do they not make tabs with less CYA for pools that already have plenty? Glad I fired the pool guy.

 

[mguzzy]

Because in a one-size-fits all world people in Florida and the North and the Pacific Northwest all get lots of rain at some point of the year and it dilutes their pool.. they are none the wiser. But for you blokes in the Southwest the rain is hard to comeby..and the CYA just builds and builds and builds and builds....you get my drift.... and builds some more.

 

[ajw22]

Why do they not make tabs with less CYA for pools that already have plenty?

Chlorine is a gas. To make a solid chlorine product you need to bind the chlorine molecules to a solid. You can bind chlorine to CYA making trichlor, or calcium making Cal-Hype, or water making liquid chlorine.

The amount of CYA is proportional to the amount of chlorine in the Trichlor.

 

[Kat-A-Tonic]

Because in a one-size-fits all world people in Florida and the North and the Pacific Northwest all get lots of rain at some point of the year and it dilutes their pool.. they are none the wiser. But for you blokes in the Southwest the rain is hard to comeby..and the CYA just builds and builds and builds and builds....you get my drift.... and builds some more.

I would double my CYA in less than a season if all I used was tabs. Does it rain enough to really displace 1/2 the water in a pool? I guess it can. Still wish the tabs could be made with less CYA somehow. Oh well, liquid it is. Thanks for all the info guys!

 

[mguzzy]

Think of the pools in Florida or the Northeast.. they get thunderstorms in the summer there all the time!

 

[Newdude]

+1. Here’s a neat map. Big difference between Nevada’s 9.5 inches of yearly rainfall and Florida with 54

 

[PointeTaken]

Does it rain enough to really displace 1/2 the water in a pool?

You'd be surprised. We got almost 40 inches of rain last March, a surplus of 36 inches over the average. We got another 25 in April, for an added surplus of 15. It was a terrible and expensive spring to be a pool owner. Even in an average spring, I have to pump out about 1/3 of my pool's volume due to rainfall.

 

[Kat-A-Tonic]

Celebratory pic of the results of getting all the stuff just right. Pic taken from 5 feet above the water of my main drain. You can see the type of screws holding the cover down. Pretty Dang clear.