Main Vents

Vents in draining systems protects traps against pressure differences that could cause them to siphon or blow out

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Vents protects traps against pressure differences that could cause them to siphon or blow out, leaving occupants unprotected against smell and potential contaminants from the sewer system.

Pipe Size
(in)		 DFU max.
(in)
1 1/4 1
1 /1/2 81)
2 24
2 1/2 48
3 84
4 256

1) No water closets permitted

  • at least one vent should terminate through the roof
  • air admittance valves within the building may be permitted (check local authority)
  • terminating vents in side wall may be permitted (check local authority)

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Related Topics

  • Dimensions - Sizes and dimensions of pipes and tubes, and their fittings - inside and outside diameter, weight and more

Related Documents

  • Vents - Stack Vents, Vent Stacks and Relief Vents

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