Why is dichlor not recommended?

[Farmingtonpool]

Gunite, 3 1/2 years old. About 30,000 gallons.

[PoolDoc]

Yes, definitely, you need a K2006 -- you not only have to manage CYA levels, but you actually need to "balance" your pool water (manage pH, alkalinity, & calcium hardness) to protect the plaster and concrete.