(1)
Except as permitted in Sentences (2) and (3), 90° elbows of NPS 4 or less whose centre-line radius that is less than the NPS of the pipe shall not be used to join 2 sanitary drainage pipes.
(2)
For sanitary drainage systems of NPS 4 or less, 90° elbows described in Sentence (1) shall only be permitted
(a)
to change the direction of piping from horizontal to vertical, in the direction of flow,
(b)
where a trap arm enters a wall, or
(c)
to connect trap arms as permitted by Sentence 7.5.6.3.(2).
(3)
A 90° elbow that is part of the pre-engineered wastewater heat recovery system is permitted to have a centre-line radius that is less than the size of the pipe.