The Drinking Water in Containers Regulations 1994

2.  the drinking water does not contain—

(a)concentrations or values of any of the parameters listed in Tables A to D in Part II of this Schedule in excess of the prescribed concentrations or values;

(b)concentrations of trihalomethanes (being the aggregate of the concentrations of trichloromethane, dichlorobromomethane, dibromochloromethane and tribromomethane) in excess of 100 μg/l;