Why Does The Pool Store Say 200 Cya Is Ok? And Problems With My K2006

[cardude]

Hey, my name is Bill. I've had pools for about 10 years but never really knew what I was doing. I got away with that on my last, smaller pool, but now

I have a 45000 gallon gunite pool and it's killing me. I'm in south Tx. and temps in the summer regularly get to 100, and the pool is in direct sunlight.

I had a hard time keeping enough FC last summer, and after reading this forum I've decided it was my high CYA causing the problem. Have been a tricolor puck chucker for years.

I bought the Taylor test kit to start to do more accurate testing, but could not really get what I thought was an accurate measure on the CYA-- my test did not even come close to the 100 mark. Took a sample to Leslies and the guy confirmed the CYA was over 100, but said he wasnt sure of exact measure. I decided to just go ahead and do a partial drain and refill, and after filling i retested for CYA and it still did not make it to 100. Frustrated, I took it to another pool store and the lady tested CYA at 132 using some kind of computer thing. I told her I was trying to get the cya to 60-70 and she asked why, said my range was fine as long as it is between 30-200. Really???

So, I guess I need some help reading the cya test on my k-2006.

I'm switching to bleach chlorination, and I'm going to try the Liquidator chlorinator in the bigger 8 gallon size to make it more automated since I'm gone in the summer quite a bit.

I'm also in the middle of my second drain and refill in a few days, so hopefully that will get my CYA under 100 at least.

What should my CYA be? Should it be a little higher since I live in a very hot and sunny area?

What should my FC levels be with a pool this size. I've had troubles of late with algae blooms.

Thanks in advance for any help yall can give me.............

[chem geek]

Many people at pool stores don't understand the relationship between Free Chlorine (FC) and Cyanuric Acid (CYA). The manufacturers don't tell them about the known science since at least 1974 that defines that relationship and the active chlorine level that is roughly proportional to the FC/CYA ratio. They don't tell them these things possibly because they want to continue to sell Trichlor products as well as very profitable high margin supplements such as algicides and phosphate removers to "solve" the problems that they would never admit are caused by having the CYA continue to climb without a proportional rise in FC.

In south Texas, you'll want your CYA level higher, probably in the 60-80 ppm range. As for the FC level, if you are manually dosing your pool, set your FC minimum target at 7.5% of the CYA level. So for 80 ppm CYA that would be a minimum FC of 6 ppm. If you lose 2 ppm FC per day, then raise the FC to 8 ppm each day or if you want to add chlorine less frequently then you can have larger swings. Even 12 ppm FC with 80 ppm CYA has the same active chlorine level as 4.5 ppm FC with 30 ppm CYA and is the same as 0.14 ppm FC with no CYA. So long as you don't drink quarts of pool water every day, you should have no problems since it is the active chlorine level that determines the rate of disinfection and oxidation. The FC level is a measure of the chlorine reserve -- the chlorine that is available to be released as it gets consumed/used.

If you are using a saltwater chlorine generator, then your FC target can be 5% of the CYA level, so a minimum of 4 ppm FC with 80 ppm CYA. The lower level is due to the continued dosing throughout the day and some superchlorination in the salt cell.

If you wanted to have a lower FC for your CYA level, then you could use a supplemental algicide such as Polyquat 60 weekly at extra cost, but it's not necessary if you maintain the proper FC/CYA ratio. You could also use 50 ppm Borates which are a mild algicide, but we don't have enough data to know how much one could lower the FC/CYA ratio, if at all. For sure, it takes the "edge" off of any potential algae growth.

[cardude]

Thanks Chem Geek! I'm almost done with my second refill and will retest after I let the pump run for a few hours.

An additional question-- is it cheaper to bite the bullet and convert to a swcg in the long run? Can I get a good one for $1000 or under? What's involved in converting?

[chem geek]

Well, your pool at 45,000 gallons is particularly large (for a residential pool) so automating chlorine dosing with a saltwater chlorine generator can be a real labor-saving device for you. It won't be cheap because you'll need a large enough SWCG to be able to handle that sized pool's need for chlorine and even the salt won't be cheap with that volume. Larger pools simply cost more to operate, period.