Direct venting more than five feet from stack

Plumbing · Venting Systems · printed page 292 (PDF page 293)

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Direct Venting More than Five Feet from Stack – Plumbing Plumbing

Text in the illustration

Direct venting more than five feet from stack the 1 1/4 drain has a slope of 1/4 per ft. and the trap is more than 5 ft. from the vent air pushes water out of trap 3 more than 5 ft. 3 vacuum forms here and creates siphoning, allowing sewer gases to enter house 2 2 lower end of the drain is flooded and air from the stack cannot prevent a siphon 1 1
the 1 1/4" drain has a slope of 1/4" per ft.
and the trap is more than 5 ft. from the vent
1
lower end of the drain is
flooded and air from the stack
cannot prevent a siphon
2
vacuum forms here and creates
siphoning, allowing sewer gases
to enter house
3
air pushes water out of trap
slope 1/4" per ft.
more than 5 ft.

Generated explanation

The illustration shows a sink with a P-trap connected by a long, sloping drain to a vertical drain and vent stack. The 1 1/4-inch drain slopes 1/4 inch per foot, and the trap is more than five feet from the stack vent. Water fills the lower end of the drain at the stack connection, blocking the air path that would prevent siphoning. Numbered annotations identify the resulting vacuum near the trap and air pushing water out of the trap, causing loss of the trap seal and allowing sewer gases into the house.

Components

sink faucet sink tailpiece P-trap trap arm drain and vent stack drain-to-stack connection

Defects shown

Trap more than five feet from the vent on a 1 1/4-inch drain sloped 1/4 inch per foot Flooded drain blocks vent air from the stack Trap siphonage Loss of trap water seal Sewer gas entry into the house

Related illustrations

1624

Direct venting

· p. 286

A lavatory sink drains through a P-trap and a sloping horizontal fixture drain into a vertical waste stack. An arrow shows drainage flowing toward the stack, and the drain is labeled with a slope of 1/4 inch per foot. A