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Main Vents in Draining Systems

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
Max. Drainage Fixture Units
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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