high CYA, but still no algae, and a few other questions...

[edavis6678]

So, my adventure with the TFT-100 and TFP forums continues!

I have a few questions if anyone can help -- denoted in BOLD

Let's start with the basics...

FC: 2-3
CC: 0
AL: 130
PH: 7.5
CH: 1250 (ya, i know)
CYA: 110-120 (ya, I know)

(I just added a tad of acid today, so the AL and PH should drop slightly to within target)

So, looking at my numbers, I know I have to drain my pool to lower the CH and CYA, although I'm hopeful with the cessation of Trichlor it may naturally drop on its own. I was going to drain it last week, but have held off for now because it's just not a good time for me to do it. (work and other chores, plus I'd like to re-plaster: so I'm holding off) -- Also, I have a July 4th party coming up and going to just live with the levels. I've stopped the use of the Trichloro Tabs and Cal-Hypo and have found a ready supply of relatively cheap 12.5% liquid chlorine. So I feel good I'm on the right path...So here are a couple questions I have regarding the information so far I've learned from TFP....

According to this chart, to maintain a pool free of algae and having properly sanitized with my current results, i need to maintain FC level around 9-13ppm.

here's what still doesn't set right...

My pool's water is visibly clear, blue and inviting, it has no algae and I constantly maintain a FC @ 2-3ppm -- how or why is it that I don't have algae or cloudy, murky, or just plain ugly water?

I really don't have much debris in my pool at all, no dead critters (outside of some bees); it gets full sun all day, and i don't heat it. (temperature currently is 75-80 degrees naturally) - it's in Southern CA, so not much rain at all.

As a theory, thinking that some of the stains on the bottom of my pool were actually algae of some type, (as mentioned in this post), I slammed my pool to 25-30ppm as an experiment to see if I saw any difference in clarity; essentially dumped the remaining Cal-Hypo i had. I don't think i technically "slammed" it correctly because i think i needed to get the CL up even higher, but all i got from this was swimmer complaining the CL was a bit too much. I will admit that maybe the stains looked a little better, but maybe just wishful thinking. (and when I asked my wife to compare from before and after, she couldn't tell the difference visually)

So...

Are my tests off or is it that the water may be clear, but is still "UN-sanitized" or deceptively still dirty? (Or perhaps not safe to swim in?)

Other than some Calcium scale on the sides of the pool, (which doesn't' seem to bother me since I just take a pumice once in a while to clean it up) - is there any other risk to leaving the CA level at 1250 for another season?

Another question regarding levels and adjustments...

So, when I use the Pool Math calculator for a rectangle pool that's 16x30 @ 8.5ft deep end, it calculates my total water volume @ 30K gallons. So the other day I went into Leslie's pool supply, (I was bored and had time to kill and wanted to tout my newly found chemistry knowledge and call them on their bullcrap), I asked them to calculate the size of my pool using their calculator. They came up with 21,000 gallons. I used the same measurements, but they also asked for the depth of my shallow end. Is there any other way to calculate the # of gallons? (outside of a full drain) - or does anyone know of another online tool that can double check my numbers?

One last question so I'm sure i have this right...

If your TC is 10, and your FC is 8, then your CC must be 2. This means that there is some bacteria in the pool that the Chlorine is fighting (they turn into Chloramines to fight bacteria), correct?

Also, CYA simply bonds to the Chlorine molecule protecting it from ultra-violet light and protects it from dissipating -- Is there is no risk to swimming in a pool with a 120+ CYA level? from this link at Taylor, it was states that the ANSI/APSP guidelines max CYA @ 100. (and a number of municipalities across the country that set that even lower) -- why is there such a regulation? Is there some risk associated with a high CYA level that I should know about?

Thanks in for reading!

 

[Wildcat]

So many questions! I will give my opinion on a few.
I think you have just been lucky. Your FC must have been higher and may have just dropped. My CYA was over 150 a year ago, and I never had algae but I used a lot of pucks and FC was high. Went to bleach but as I live in the desert I am reluctant to do a big drain and refill. In the past year I have dropped CYA to around 100. I just keep my FC at safe level 8-12 PPM. I will wait for our monsoon season next month and drop the water a foot and let the rain help replace some to drop CYA more.

Not a pool store advocate but you do need to factor in the shallow and deep end measurements to get sort of an average depth. Their calc is probably more accurate if you only used the deep end in your calc.

- - - Updated - - -

BTW, everything I read says CYA will not drop on its own and no chemical way to reduce it either.

 

[Kiss4aFrog]

The way to reduce CYA is to replace water Higher CYA will cost you in having to maintain higher FC levels.
The way to reduce CH is to replace water Higher CH could cause a build up of scale.

You should be keeping the FC level 7-12 because of your high CYA level. The higher the CYA, the higher the FC level needs to be to properly sanitize the water.
http://www.troublefreepool.com/content/128-chlorine-cya-chart-slam-shock

Multiple volume calculators: https://www.google.com/#q=pool+capacity+calculator+gallons

The regulation on CYA might be because of how much more chlorine needs to be in the water to keep it sanitized. At some point in a commercial application you'd need to have a taker bleeding chlorine in to make up for what's getting used but I'm just guessing.

 

[JasonLion]

The risk of high CYA levels is that CYA reduces the active level of chlorine. This can be countered with extremely high FC levels, but you have not done so, so your pool is effectively not sanitized.

When using PoolMath to calculate the pool volume you are supposed to use the average depth, not the deepest depth.

If you think of calcium scaling as something that you take a "pumice once in a while to clean it up", they you haven't had real calcium scaling. Serious calcium scaling, which is getting very likely given your CH level, is not something that is easily rubbed off with a pumice stone.

 

[toddcudd]

In case it helps: 1/2 of my pool is "shallow end" - 3 ft. Then it drops 3 to 6, sloped nearly to the end. So my average is (3 + (3 + 6)/2)/2 = 3.75. I average the deep end, add it to shallow end, and divide by 2.

 

[Kiss4aFrog]

Settle on a number for your volume. Find a parameter that you need to change, pH, FC, TA by adding something. Test your water to find out where you are, add the exact amount of chemical the calculator tells you to, let it mix and retest. Try it a couple times and see if you can hit the number the calculator says you should. If you come up over your pool is likely smaller and if you come up short it's bigger. It's how I figured out how big my old spa was.