[AS.] A contrivance to prevent the passage of offensive gases along a drain. The siphon trap, which is perhaps the best and simplest, is merely a bend in the pipe, which remains filled with water. There ought to be traps placed where the pipes from the inside of the house join the drain, and there should also be a trap j ust where the drain joins the sewer. But drains and sewers ought both to be ventilated - to have openings for the bad gases to escape.

TRAP.

TRAP.