Minimum size of vent required

[MasterPlumbersKeymaster]

I need to run a new vent for a water closet, lav and bar sink. There is an existing 2″ vent for another water closet and lav. Can I connect to this vent is my question???

[SylvanLMPParticipant]

Ah Mike dont you just wish plumbing were that simple guy?

Venting is not just fixture units connected BUT developed lenth of pipe and fittings.

For example I could run 8 FU’s on an 1-1/2 line BUT only for 30 ft BUT I would need a 2″ line to go up to 170 ft.

Did you now depending on what type of toilet you have how many fixture units it is rated at?

For example a close couple tank and bowl would be 4 FU and a flushometer type would be 6 FU..

Why dont you invest in a local code book rather then guessing?

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SylvanLMP

[GuestParticipant]

Its to bad plumbers do not have a code book thats close to the same in this country. Respect comes from organisation. In CT you can vent 102 DFU (16 bathrooms) on one 1 1/2 vent pipe 30 ft.

[Robert Stephen MortonParticipant]

Mr Unity. We lowly Plumbers in Oz work on a rating system for vents, that is :-

Size of Fixture units Vent rating
vent pipe discharging to
DN drain

40 >1 <10 .5
50 >10 <30 1
65 >30 <175 2
80 >175 <400 3
100 >400 6

If there are other vents on the line they can be used as credits. ie 12 40mm vents off a stack could be equivelent to a 100mm vent venting more than 400fu, However we have to get the sewage to run uphill.

[SylvanLMPParticipant]

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In reply to message posted by unity:
Its to bad plumbers do not have a code book thats close to the same in this country. Respect comes from organisation. In CT you can vent 102 DFU (16 bathrooms) on one 1 1/2 vent pipe 30 ft.

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Is this a local code like Danbury or a state code?

102 FU’s seems like a lot on a 11/2 pipe ESPECIALLY in a movie theater where it would be quite possible all fixtures being used at once during an intermission.

The over loading of the vent would be unbelievable with back pressures.

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SylvanLMP

[Author]

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