13(1)A hereditament is exempt to the extent that it consists of any of the following—
(a)a sewer;
(b)an accessory belonging to a sewer.
(2)“Sewer” has the meaning given by section 343 of the [1936 c. 49.] Public Health Act 1936.
(3)“Accessory” means a manhole, ventilating shaft, pumping station, pump or other accessory.
(4)The Secretary of State may by order repeal sub-paragraphs (1) to (3) above.