TA recommended level question

[Woodberg]

For an inground concrete pool, why is the recommended level of TA 70-90 when using bleach and 100-120 when using Trichlor?

[JasonLion]

Trichlor is acidic, and is constantly lowering both the PH and the TA. In order to keep the PH from falling too quickly the recommended TA level is higher.

When using bleach, which is PH neutral in the long run, the dominant effect of TA is to slowly push the PH up as CO2 outgases. To minimize this effect the recommended TA level is lower.