Mitsubishi Heavy Industries SRK25GZ-L1 Handbook page 168

SCM-HG (4 room)
4) Use hard PVC general purpose pipes VP-25 sold on the market
for drain pipes after draining up.
5) Tighten the PVC pipe securely with the attached clamp after
inserting it in the drain socket.
6) The drain pipe must have downward inclination gradient of 1/
100 or more, and take care not to make a trap or uphill pass.
7) When connecting the drain pipe, take care not to apply force on
the pipe of the unit, and clamp the pipe as close as possible to
the unit.
8) Don't attach air purge pipe, because the drain might spout.
9) Be sure to provide heat insulation to the indoor side drain pipe.
166
3 Hose clamp
Drain hose
Down gradient
(1/100 or more)
Up hill
pass
Trap