The shapes of traps vary, and the number of the various kinds of traps manufactured is very great.
Traps are named according to their use: gully, grease, sediment, intercepting, etc.; according to their shape: D, P, S, V, bell, bottle, pot, globe, etc.; and according to the name of their inventor: Buchan, Cottam, Dodd, Antill, Renk, Hellyer, Croydon, and others too numerous to mention.
The S trap is the best for sink waste pipes; the running trap is the best on house drains.
Fig. 19.
FORMS OF TRAPS.
Fig. 20.
FORMS OF TRAPS.
Loss of Seal by Traps.—The seals of traps are not always secure, and the causes of unsealing of traps are as follows: