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Schematic of a direct vented plumbing fixture (C) Carson Dunlop AssociatesPlumbing Vent Distances & Routing Codes

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Plumbing vent distances, routing, clearances:

This article gives recommended or allowable distances from plumbing vent to fixtures, distdances from plumbing vent to building features like chimneys, windows, roofs, walls.

This article series includes definitions of plumbing vent terms, types of plumbing vents, plumbing vent size requirements, plumbing vent clearance distances to building roof, vertical walls, nearby windows, or plumbing vent distance to chimneys. We explain how plumbing vents work on buildings, why plumbing vent piping is needed, and what happens to the building drains when the vent piping is not working.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

Plumbing Vent System Distances & Routing

Plumbing vent terminology sketch (C) Carson Dunlop Associates The basic plumbing vent terms are shown in the sketch at above/left. In these notes, the plumbing stack vents and other sketches included below are provided courtesy of Carson Dunlop Associates. [Click to enlarge any image]

Article Contents

Basically,larger piping diameter allows longer distances between a plumbing fixture and its vent stack. If a plumbing fixture is located too far from the main building vent stack, then its own drain pipe must have its own vent stack connection piping.

The usual slope on the fixture drain piping is 1/4" of slope per 12" (foot) of horizontal distance or "run" of piping.

Distances: How far can the plumbing vent piping be located from a plumbing fixture?

Schematic sketch of distance allowed between a plumging fixture and vent piping (C) Carson Dunlop Associates

As we discuss at PLUMBING DRAIN NOISE DIAGNOSIS, if the horizontal distance between a plumbing fixture and the vertical vent piping is too great, the fixture may not drain properly, producing slow drainage or gurgling noises.

Poor drainage is not just an annoyance, it can be unsafe since there is also the risk that the poorly-vented plumbing fixture will lose the water from its plumbing trap, then permitting sewer gases into the building.

As we show in Carson Dunlop Associates' sketch, the distance allowed between a plumbing fixture (actually the fixture plumbing trap) and the vertical vent piping varies between a minimum and maximum as a function of the pipe diameter.

Tables of Plumbing Drain Pipe & Vent Pipe Sizes & Critical Distances to Plumbing Fixtures

Below our tables 1 and 2 summarize common plumbing code specifications for fixture venting and vent pipe sizes and distances that a plumbing fixture can be located (horizontally) from the vent stack. You'll see these distances also in our sketch at left. [Click any image to see an enlarged, detailed version.].

Table 1. Plumbing Drain Pipe Sizes
Drain Pipe Diameter Vertical Drain Pipe, Maximum Number of Fixtures Horizontal Drain, Maximum Number of Fixtures
1-1/4" dia 1 1
1-1/2" dia 2 1 (or 2 sinks)
2" diam 16 8
2-1/2" dia 32 14
3" diam 48 35
4" diam 256 216
Note: you can see from this table that at common home drain pipe sizes, if your pipe is 2" or larger you're unlikely to run into drain capacity trouble.

...

Table 2. Vent Pipe Distances
Drain Pipe Size Vent Pipe Size[1] Distance [2]
1-1/4" diam 1-1/4" diam 2-1/2 feet
1-1/2" diam 1-1/4" diam 3-1/2 feet
2" diam 1-1/2" diam 5 feet
3" diam 2" diam 6 feet
4" diam 3" diam 10 feet

[1] minimum diameter of the vent pipe

[2] Critical distance between the plumbing fixture and the vent pipe. You can see that for vent pipe diameters under 4" you need to be vigilant about locating a plumbing fixture too far from its vent pipe/stack

Plumbing Vent Routing Specifications

Within the building the plumbing vent routing is generally unrestricted.

That is, dry vent piping carrying only air, sewer gas, or moisture to above the roof line is unrestricted. However the piping does need to be protected from nails - use nail plates to protect vent and drain piping both where where piping passes through studs, joists, or rafters.

Special routing and connections are required for proper venting of plumbing fixtures such as kitchen island or peninsula sinks or dishwashers - plumbing fixtures that are located where a direct vertical vent stack connection is not possible.

See ISLAND SINK PLUMBING VENTS for details.

Table of Plumbing Vent Clearance Distances to Building Features

The table below gives required clearance distances to various building features and cites pertinent model plumbing codes.

Building Feature

Required Distance from Plumbing Vent Termination to Building Feature

Comments

Roof Surface, distance to Plumbing Vent 6-inches above nearest roof surface "nearest" accommodates sloped roof - i.e. measure from the "up-roof" side.
Nearest vertical surface, distance to plumbing vent 12-inches from nearest vertical surface such as the side-wall of an upper story on the building

Nearest window, door, opening, air intake, or ventilation shaft: distance to plumbing vent.

 

10 ft (120-inches) from nearest window, measured horizontally

- OR -2 ft. (24-inches) above nearest window [or other opening listed at left], measured vertically
We interpret this rule to apply to the required separation distances between a plumbing vent and nearest chimney on the building - Ed.
Distances are measured horizontally unless we indicate otherwise

Plumbing Code Citations for Plumbing Vent or Vent Stack Clearance Distances

Quoting the IRC model plumbing code

12.4 VENT TERMINALS

12.4.1 Extension Above Roofs

Vent pipes shall terminate not less than 6 inches above the roof, measured from the highest point where the vent intersects the roof. EXCEPTION: Where a roof is used for any purpose other than weather protection, vents shall extend at least 7 feet above the roof and shall be properly supported.

12.4.4 Location of Vent Terminal

a. Vent terminals shall not be located where vapors can enter the building.

b. No vent terminal shall be located directly beneath any door, window, or other ventilating opening of a building or of another building,

nor shall any such vent terminal be within 10 feet horizontally of such opening unless it is at least 2 feet above the top of such opening.

c. Where a vent terminal is within 10 feet horizontally and less than 2 feet above a ventilation opening described in Section 12.4.4b

and the line-of-sight from the vent terminal to the ventilation opening is interrupted by the continuous ridge of a roof, the ridge shall be at least 2 feet above the top of the opening. Otherwise, the vent terminal shall comply with Section 12.4.4b.

d. Where a vent terminal is within 10 feet horizontally and less than 2 feet above a ventilation opening described in Section 12.4.4b and the line of sight from the vent terminal to such ventilation opening is interrupted by a solid wall or solid barrier, the top of the wall or barrier shall be at least 2 feet above the top of the ventilation opening

and the shortest travel distance around the wall or barrier from the vent terminal to the nearest edge of the ventilation opening shall be at least 10 feet. Otherwise, the vent terminal shall comply with Section 12.4.4b.

Plumbing Code full-text on Plumbing Vent Codes

Code Citations for Plumbing Vent Terminals at the Rooftop or Through Walls

904.1 Roof extension. All open vent pipes that extend through a roof shall be terminated at least [NUMBER - typically 6 ] inches (mm) above the roof, except that where a roof is to be used for any purpose other than weather protection, the vent extensions shall be run at least 7 feet (2134 mm) above the roof.

904.2 Frost closure. Where the 97.5-percent value for outside design temperature is 0ºF (-18ºC) or less, every vent extension through a roof or wall shall be a minimum of 3 inches (76 mm) in diameter. Any increase in the size of the vent shall be made inside the structure a minimum of 1 foot (305 mm) below the roof or inside the wall. 

904.3 Flashings. The juncture of each vent pipe with the roof line shall be made water tight by an approved flashing.

904.4 Prohibited use.Vent terminals shall not be used as a flag pole or to support flag poles, television aerials or similar items, except when the piping has been anchored in an approved manner. 

904.5 Location of vent terminal. An open vent terminal from a drainage system shall not be located directly beneath any door, openable window, or other air intake opening of the building or of an adjacent building,

and any such vent terminal shall not be within 10 feet (3048 mm) horizontally of such an opening unless it is at least 2 feet (610 mm) above the top of such opening.

904.6 Extension through the wall. Vent terminals extending through the wall shall terminate a minimum of 10 feet (3048 mm) from the lot line and 10 feet (3048 mm) above average ground level. Vent terminals shall not terminate under the overhang of a structure with soffit vents.

Side wall vent terminals shall be protected to prevent birds or rodents from entering or blocking the vent opening.

904.7 Extension outside a structure. In climates where the 97.5-percent value for outside design temperature is less than 0ºF (-18ºC), vent pipes installed on the exterior of the structure shall be protected against freezing by insulation, heat or both. 

Plumbing Codes, Citations, Fulltext Codes, & Plumbing Code References

Watch out: while the 2015 IPC is the most-recent version of the International Plumbing Code, while the 2018 IPC is under development. To understand which generation of the model building code or plumbing code applies to your specific project you will need to check with your local building official. For example many jurisdictions are on the 2012 IPC or still older versions.

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Continue reading at PLUMBING VENT DEFINITIONS, TYPES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see AIR ADMITTANCE VALVES AAVs - Studor Vents Explained

Or see PLUMBING DRAIN FIXTURE UNITS DFUs - drain fixture units or DFUs defined & explained + table of DFUs

Or see PLUMBING VENT FAQs - questions & answers about plumbing vents

Or see PLUMBING DRAIN NOISES where we explain the basics of proper plumbing vent piping and how errors cause trap siphonage, odors, and noises

Or see PLUMBING VENT DEFECTS & NOISES - home

Or see this

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