(1) This regulation applies if—
(a) the drainage system of a dwelling or building (the first dwelling or building ) is combined with the drainage system of a dwelling or building on another parcel of land; and
(b) the combined drainage system is in the other parcel of land; and
(c) the combined drainage system was installed before 1 March 1999; and
(d) significant work has to be done on the drainage system of the first dwelling or building.
(2) A person doing significant work must—
(a) disconnect the existing drainage pipes from the combined drainage system; and
(b) if no separate drainage system is in place for the dwelling or building—install a separate system; and
(c) connect the first dwelling or building to that drainage system.
(3) In this regulation:
"significant work" means work where—
(a) drains to more than half the fixtures are altered; or
(b) the number of fixtures is increased by more than 50%.