49 vent stacks are used only to allow air to enter

49. Vent stacks are used only to allow air to enter the system
50.The fixture branch is the horizontal pipe running from the fixture trap to the
vertical soil or waste stacks
51. Hydraulic Grade is a line from the water level of a fixture such as the lavatory to
the branch connection at the soil stack.
52. Individual vent is sometimes referred to as back vent.
53.It is that portion of the vent pipe which serves a single trap.

54. Individual vent is the most practical vent of trap which effectively prevents the
minus or plus pressure of every fixture trap.
55.No vent should be less than 38mm (1 ½”) diameter except for a 32mm (1 ¼”)
waste.
56.All branch vent pipes should be free from drops or sags and should be so graded
and connected so as to drip back the soil or waste pipe by gravity.
57. Circuit or Loop vent is employed where two or more fixture traps are installed on
a horizontal soil or waste branch, generally reduces the cost of plumbing
installation.
58. Main vent – the principal artery of the venting system to which vent branches are
connected.
59. Individual vent – is a pipe installed vents a fixture trap and which connects with
the vent system above the fixture, serve or terminate in the open air
60. Unit vent – an arrangement of venting or installed that one vent pipe will serve
two trap.
61. Circuit or Loop vent – a group vent pipe which starts in front of the extreme
fixture connection on a horizontal branch or connects to the vent stack.
62. Yoke vent – a pipe connecting upward from a soil or waste stack below the floor
and below horizontal connection to an adjacent vent stack at a point above the
floor and higher than highest spill level of fixtures for preventing pressure
changes in the stack.