Newbie - Reading Pool School and I am Confused!

[gooselover]

I posted on pool opening and closing about cloudy water. You advised me to read Pool School and I am. However, I am confused about the CYA in correlation to FC and CC = TC.

If stablizer HELPS keep the free chlorine from being burned off, how can too much CYA require you to add more chlorine to maintain it's effectiveness?

Can someone explain this?

During the last three years of our pool being in operation, I have consistently used shock 1x a week, 1 3" tab in the skimmer (usually 1 or 2 a week) and checked the PH and TA. Truthfully, it was a piece of cake keeing the pool clear, but now, this year, I am having trouble (had green murky water).

So, can someone explain this? Thanks!

 

[JasonLion]

CYA binds to some percentage of the chlorine, which both protects it from sunlight and also prevents it from helping sanitize your pool. That leaves less active chlorine in the water to keep things sanitary. To keep the active chlorine level the same when you raise your CYA level, your need to raise the FC level.

CYA always binds to some percentage of the chlorine. If the active chlorine gets used up, some of the bound chlorine will unbind and become active. In effect, CYA creates a chlorine reserve.

 

[CosmicJester]

Cyanuric acid acts as sort of a traffic cop for the chlorine. Without it, all the chlorine gets burned off by sunlight in minutes. If you have too much CYA in the pool, it keeps the chlorine in the pool too well and won't let the free chlorine do its job of sanitizing the water. So, you have to add more chlorine to compensate. Using tabs consistently adds CYA to the pool, and eventually you get stuck in the situation you are now, where the pool has plenty of chlorine but the water is still green. Also, the granular shock treatment (note that shock is a verb, not a noun) is often calcium hypochlorite, aka cal-hypo. This adds calcium to your water, and bumps up your CH level. You need some CH in your pool, but too much gives you ugly murky water. Run a full test on your water (FC, pH, TA, CH, CYA) and report back. I'd be willing to bet your CYA level is through the roof.

 

[fuzzy_dba]

...cloudy water...confused about the CYA in correlation to FC and CC = TC.
If stablizer HELPS keep the free chlorine from being burned off, how can too much CYA require you to add more chlorine to maintain it's effectiveness?
During the last three years of our pool being in operation, I have consistently used shock 1x a week, 1 3" tab in the skimmer (usually 1 or 2 a week) and checked the PH and TA. Truthfully, it was a piece of cake keeing the pool clear, but now, this year, I am having trouble (had green murky water).

I'll give this one a shot, using the information is Pool School.
CYA acts as a "shield", preventing your FC from burning off in the sun. If there is too much CYA your FC levels have to be higher and higher to prevent algae (sanitize), much less kill it if it's already there (shock it). Simply put, the chlorine chemically binds itself to the CYA leaving FC to sanitize. The more CYA, the higher FC level is required.
See the chart in pool school:
http://www.troublefreepool.com/pool-school/chlorine_cya_chart_shock

What this shows is that the amount of FC that you have to maintain, at a minimum, increases as the CYA increases. In particular, look at the Shock FC levels: For a CYA of 40 the shock level is 16. When the CYA has gotten up to 80 (2x as much) the amount of FC required to shock the water doubles as well.

Have you been using calcium hypochloride in the bags as well as pucks? If that's the case you may have very high calcium levels in addition to high CYA levels.

What are the FC, CC, PH, TA, and CYA levels of your pool now?
What are you using to measure the water?

 

[gooselover]

When I tested the water around noon, all levels were right on with the exception of the CYA or stabilizer (using AquaChem test strips). The stabilizer has ALWAYS been at 0 - even previous years. Still shows 0.

However, you made sense on my question regarding CYA and Chlorine - perfect sense.

And one more question, Borax is to raise PH ONLY, doesn't have anything to do with CYA, correct? What is confusing is on Page 2 of 2 on the Pool School "What is BBB", it specifically states "They sell it as a water condition to help STABILIZE ph and prevent algae.

I think that is where I, and some others got confused on it being a PH increaser AND a stabilizer.

 

[JasonLion]

Your test strips are almost certainly wrong. It is fairly common for test strips to give wildly incorrect results on CYA.

The word "stabilizer" gets used for various things, as does the word "conditioner", so there is often some ambiguity. CYA stabilizes chlorine against sunlight. Borates buffer PH against changes. It is also confusing that borax is used for two different things, raising the PH and adding borates to the water.

 

[fuzzy_dba]

...all levels were right on with the exception of the CYA or stabilizer (using AquaChem test strips). The stabilizer has ALWAYS been at 0 - even previous years. Still shows 0.

I did the same thing that you did, and tested with test strips. After all, why would they sell them if they were not accurate, right?
What I found, after a green pool and using a decent (but not good) test kit, was that:
The CYA was well over 100 even thou the test strips said it was OK.
The chlorine level was very low and not sanitizing the pool; test strips said it was high!
The PH was over 8.0; the test strips said it on the high end of "OK" too.
I'll never again use test strips except to test salt levels in the pool.

I'd strongly recommend the Taylor 2006 or the TF100 kit (a bargain! http://www.tftestkits.net/). Testing your water with the drop test kits doesn't take much longer than the test strips (about 5 minutes/day) but you really know what's going on in your pool.
When you know what's going on it's easy to make minor changes. I just shock my pool when I open it and close it, and add some extra chlorine when I know that there's going to be a party (extra swim load). During the swim season it doesn't need the extra chemicals.