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;

• rain-water drainage includes gutters, pipes, drains and fittings which convey rain-water only;

• sanitary appliance has the meaning assigned to it by regulation P1;

• 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.

Regulation N5 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 rain-water from another part of a building.