40 CFR § 141.54 - Maximum residual disinfectant level goals for disinfectants.

MRDLGs for disinfectants are as follows:

Disinfectant residual	MRDLG(mg/L)
Chlorine	4 (as Cl 2).
Chloramines	4 (as Cl 2).
Chlorine dioxide	0.8 (as ClO2)

[63 FR 69465, Dec. 16, 1998]