The Cal-Hypo conversation in Chem 201 got me to thinking about trichlor cost verus bulk stabilizer. Does this analysis look correct?
From chemgeeks post, a 10ppm increase in FC relates to a 6ppm increase in CYA.
My pool is 24k gal. It takes a 3.7 ppm increase to get me to 182 oz of bleach. A 182oz jug is around $2.50 if memory serves. It takes 13 oz of trichlor to be the equivalent to the 182. There is probably some rounding on that 13 number and since we're rounding the little number instead of the big one, it might void the analysis....I'll continue anyway.
10ppm of FC = 6 ppm of cya, thus a ratio of 0.6, so .6*3.7 FC = 2.22 ppm of CYA. It takes 6.4 oz of CYA to increase 2.22ppm.
From aquasuperstore, it's $35 for 10# of trichlor or 3.5$/#. It's $39/8# of stabilizer at Leslies or $4.875/#.
To get 13oz of CL from trichlor you have 13/16*3.5 = $2.84 which is a little more than the bleach. You get 6.4 oz of CYA for "free"
To get 6.4oz of CYA from bulk you have 6.4/16*4.875 = $1.95.
So, if you're short of CYA and work the number back from a 1 jug equivalent, you'd have $2.50 + $1.95 = $4.45 for bleach or $2.84 for trichlor alone.
Let's relate $/ppm of CYA, tri: $2.84/2.22 = $1.28/1ppm; bulk: $1.95/2.22 = $0.88/ppm. So, if you're a swg person and rarely use bleach (but do on occaision) like me then it makes sense to keep buyiing bulk stabilizer and grabbing a jug of bleach when needed. If you're using lots of bleach then it looks like it makes sense to supplement with trichlor at the beginning of the season.
Am I missing anything?