Hong Kong Regulations

BUILDING (STANDARDS OF SANITARY FITMENTS, PLUMBING, DRAINAGE WORKS AND LATRINES) REGULATIONS - REGULATION 49

Junctions of drains

(1) The junction of a single branch drain with another drain at an angle of
not more than 45o in the direction of flow may be made by means of a
purpose-made Y junction.

(2) The junction of every other branch drain with another drain shall be made
within a manhole, obliquely at an angle of not more than 60o in the direction
of flow of such other drain, and shall be above the invert of such other
drain.