On Sat, 20 Apr 2013 22:14:14 +0000 Danny D. wrote:

Assuming the Costco available percentage is reasonable, it seems
the way to go (at $2/pound); but was just wondering if SMS knew
the best place to buy about 100 pounds of 3 inch trichlor tablets.

I bought the Costco trichlor tablets but found out it's 85% effective.
I also found out that we only have two effective percents for trichlor.
1. There's 90% available chlorine
2. And then there's 85% available chlorine

Price for working free chlorine should determine which you choose,
since there isn't really any other difference (other than some are
wrapped individually which I would find to be a pain).

- Costco & Lowes = 85% available chlorine
- Leslies & Home Depot = 90% available chlorine

So, my rough draft table is the following (unconfirmed yet):
- Costco $80/40 pounds * 100/84.65 pounds = $2.36/pound FC
- Leslies $80/35 pounds * 100/90.0 pounds = $2.54/pound FC
- Home Depot $60/24 pounds * 100/90.0 pounds = $2.78/pound FC
- Lowes $60/24 pounds * 100/84.95 pounds = $2.94/pound FC

Interestingly, we find the HASA liquid chlorine, even at the web
sale price of buy-1-get-1-for-just-tax in that same cost range:
$21.62/8gal x 1gal/9.7pounds x 1/10.8% by wt avail Cl = $2.58/pound FC

Of course, the solid trichlor increases the cyanuric acid in the
pool at about the rate of 1.73ppm/pound while the liquid chlorine pushes
up the pH necessitating a bit more acid ... so there are additional
considerations other than straight cost per free chlorine to consider.