78.—(1) Regulation 82 shall not apply to a drainage system intended for use in connection with a roof or balcony of 6 m2 or less in area, unless that roof or balcony receives a flow of rainwater from another part of a building.
(2) In this Part—
“Foul water” means waste from a sanitary appliance and water which has been used for cooking or washing purposes and not contaminated by trade effluent;
“Rainwater drainage” includes gutters, pipes, drains and fittings which convey rainwater only;
“Sanitary appliance” has the meaning assigned to it by regulation 84 in Part P;
“Sanitary pipework” means a pipe or system of pipes for conveying foul water from a fitting to an underground foul drain; and
“Underground foul drainage” includes drains and private sewers used in connection with buildings but not a system which is solely for the conveyance of subsurface water.