Fitting Fixtures and Services

Fittings, Fixtures And Services 3(1+2)

Lesson 10 : Water supply system, drainage system and drainage bye laws

Types of Traps

Venting
If a negative pressure develops in the drain-pipe beyond a water trap, it is possible that water will be drawn out of the trap which is then rendered ineffective. In a similar manner, if a positive pressure develops in a drain- pipe it is possible for water to be forced out of a trap into the appliance. One way in which this can be done is to fit each appliance drain with an individual vent. At a level above the connection of the highest appliance drain, the vent pipe is connected to the drain pipe, which is extended to roof level where it opens to atmospheric pressure.
In some cases , particularly where appliance drains are short and where a group of appliances are connected in a cluster around a drain pipe which opens to the atmosphere at roof level, individual vents are not required.