Where to buy CYA? & acid ?

I bought baking soda at Costco 13.5lbs for $7, then off to walmart for borax 4lbs12oz @ $3.50 a box. Muriatic acid from home depot was $7 a gallon, is that a good deal? It was called safer muriatic acid from Kleen strip, is that the same stuff. The guy behind the paint counter said they weren't allow to sell regular muriatic acid in NY anymore. Can you buy CYA anywhere besides a pool supply store? They wanted $10 for a 4lbs bag, is that reasonable? Also my aqua rite manual says I need 12lbs for a 18K pool but, the bags say 3lbs for every 10K which works out to 5.4lbs. Which is right?
Thanks for all your help

You can get CYA from lots of places, WalMart (in the spa section), Home Depot, Lowe's, most anywhere that sells pool stuff. Just check the ingredient label and make sure that the ingredient is cyanuric or isocyanuric acid. If there's a bunch of other stuff listed, skip that one--these days the chemical companies are putting a lot of "mystery goop" into what used to be plain chemicals--that way they can advertise them as "dual action", etc. You don't want mystery goop. :) As far as the dosing, I would base it on what CYA level the SWCG folks want you to maintain, then figure out how much you need from there.

Check the ingredient label on the muriatic--I'm sure it's fine, but check just to make sure. The full-strength stuff is 31% but I think they're also selling a lower percentage concentration of it, too, which is fine. That price would be a little high down here, especially if it isn't the full-strength stuff, but up in your area of the country it's probably about average. I don't know whether you folks have Tractor Supply Co chain stores there, but if so, it's the cheapest place down here to get it--and it's the full-strength stuff. I think I paid around $5.50/gallon for it the last time I bought it.

By the way, the CYA may be labeled as stabilizer or conditioner but will still say cyanuric or isocyanuric acid as the ingredient.

Of course there isn't anything on the muriatic label http://www.wmbarr.com/ProductFiles/G...06%20J5807.pdf so I had to start searching and found out it's <25% hydrochloric acid http://www.wmbarr.com/ProductFiles/K...%206-10-08.pdf
How many ounces of muriatic acid per 10K gallons to lower PH?
Also the Aqua rite manual says the CYA should be between 60-80 ppm, I thought I read somewhere on here that it should be between 30-50ppm. The bag at the store said between 35-100ppm. Also the 12lbs called for in the aqua rite manual was to raise it to 80ppm.

How many ounces of Muriatic acid to lower your pH will depend a lot on your TA--the higher the TA, the more acid it will take to drop the pH than at a lower TA. It also will depend on how low you want to drop it. With a SWCG, though, dropping your pH is going to be a continual thing, and the acid lasts a long, long time, so I would go ahead and get a gallon of it and you can go from there.

Regarding your CYA, go with what your SWCG manual says. Each model requires a different amount, and it is designed to extend the cell life and let the unit work the most efficiently, so that's what you want to go with--and I believe the SWCG gurus on this forum say that you need to be at the high end of that range.

Thanks for all the help