r. 15
(1) Drainage work is—
(a) the construction, installation, replacement, repair, alteration, maintenance, testing or commissioning of any part of a below-ground sanitary drainage system or a below-ground stormwater drainage system from the above-ground sewage, stormwater or waste pipes to the connection with the disposal system; and
(b) any design work that is incidental to, or associated with, any work described in paragraph (a).
(2) Drainage work does not include—
(a) the construction, installation, replacement, repair, alteration, maintenance, testing or commissioning of—
(i) a subsoil drain for the sole purpose of subsoil water collection; or
(ii) stormwater pits, channels that are grated or below-ground storage or retention tanks; or
(b) any design work that is incidental to, or associated with, the work described in paragraph (a).