How much CYA does Trichlor add to a pool?

[mgoeckner]

This is an issue I have with my pool and I THINK I have the answer.

Adding 1 lbs of 100% TriChlor (trichloro-s-triazinetrione) to a 10,000 gallon pool will give you 18 ppm Cl and 11 ppm of CYA. (These numbers come indirectly from "Pool & Spa Operator Handbook"...)

Thus - a 35 lbs box of 90% TriChlor will add 338 ppm.... to a 10,000 gallon pool. OUCH!

Someone please tell me if this is wrong.


Pool & Spa Operator Handbook - https://www.amazon.com/Pool-Spa-Oper.../dp/0984586377

[PoolDoc]

Trichlor is about 50% CYA, by weight.

A 10K pool has a pool factor of 12.

So, a 1lb dose of trichclor will add 0.9 x 12 ppm of chlorine and 0.5 x 12 ppm of CYA, or 11 ppm chlorine and 6 ppm of CYA.

6 x 35 is 210, not 338.

BUT . . . yes, trichlor adds a lot of CYA. On pools that leak a lot, this may not be a problem. But with pools that have low leakage and high chlorine demand, CYA levels can build up very rapidly. That's why most pools need to use a mix of dichlor/trichlor (with CYA) and bleach / cal hypo (without CYA).