John Lansing
@pipedreaming.bsky.social
Plumbing, building codes, engineering design guides, water and nutrient cycle, architecture, embodied carbon, development, cities, and the international variations of them all
The explanation for why WCs are prohibited in Section 913 is very limited, but the problem poses no real issues in a 4 inch drainage stack, except in very tall buildings. What’s funny is WCs are allowed in Section 917, but the stack base clearance zone poison pill applies.
![913-WASTE STACK VENT
913.1 Waste stack vent permitted. A waste stack shall be considered to be a vent for all of the fixtures discharging to the stack where installed in accordance with the requirements of this section.
C A waste stack vent uses the waste stack as the vent for fixtures other than urinals and water closets. The principles of use are based on some of the original research that was done in development of the first plumbing codes. The system has been identified by a variety of names, including vertical wet vent, Philadelphia single-stack and multifloor stack venting. Note that due to the oversized design of a waste stack vent system, a vent stack is not required and thus, a relief vent is not required (see Section 904.2, Exception).
913.2 Stack installation. The waste stack shall be vertical, and both horizontal and vertical offsets shall be prohibited between the lowest fixture drain connection and the highest fixture drain connection. Fixture drains shall connect separately to the waste stack.
The stack shall not receive the discharge of water closets or urinals.
C Because the drainage stack serves as the vent, there are certain limitations on the design to prevent pressures in the system from exceeding plus or minus 1 inch of water column (249 Pa). The system is identified as a waste stack vent because it prohibits the connection of water closets and urinals. Only waste may discharge to the stack.
Water closets and some urinals have a surging discharge that results in too great a pressure fluctuation in the system.
The system can serve sinks, lavatories, bathtubs, bidets, showers, floor drains, drinking fountains and standpipes.
To preserve the desirable annular flow in the [text overrun]](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:zrfppf44vjnvtplygmvbk5we/bafkreidrxuongawimu7pb75p2nxzfnaddbvn52o5jju5mdcnsyxjc3d4aq@jpeg)
November 25, 2025 at 3:39 AM
The explanation for why WCs are prohibited in Section 913 is very limited, but the problem poses no real issues in a 4 inch drainage stack, except in very tall buildings. What’s funny is WCs are allowed in Section 917, but the stack base clearance zone poison pill applies.
Even Canada allows the vent piping to be eliminated for installations like this, which is essentially a single stack that prohibits WCs. Good enough for Copenhagen, London, Frankfurt, Vancouver, Paris, Miami, and Nashville but not NYC, San Francisco, Seattle, Houston, Los Angeles, ect.
November 25, 2025 at 3:19 AM
Even Canada allows the vent piping to be eliminated for installations like this, which is essentially a single stack that prohibits WCs. Good enough for Copenhagen, London, Frankfurt, Vancouver, Paris, Miami, and Nashville but not NYC, San Francisco, Seattle, Houston, Los Angeles, ect.
Can’t say if this installation was under the 1938 NYC building code or the 2022. 🙃
November 25, 2025 at 3:19 AM
Can’t say if this installation was under the 1938 NYC building code or the 2022. 🙃
By increasing the diameter of the drainage stack for a kitchen sink from 2 inches to 3 inches, all of the vent piping can be eliminated. This isn’t however allowed in most major American cities. NYC adopted the International Plumbing Code but deleted sections 913 and 917 that would allow this.
November 25, 2025 at 3:19 AM
By increasing the diameter of the drainage stack for a kitchen sink from 2 inches to 3 inches, all of the vent piping can be eliminated. This isn’t however allowed in most major American cities. NYC adopted the International Plumbing Code but deleted sections 913 and 917 that would allow this.
Not once have I seen this compact arrangement of plumbing fixtures in a double loaded corridor building. I see this all the time in single stair buildings though. This can eliminate so much lost energy waiting for hot water, as well as water supply and drainage piping.
November 23, 2025 at 6:47 PM
Not once have I seen this compact arrangement of plumbing fixtures in a double loaded corridor building. I see this all the time in single stair buildings though. This can eliminate so much lost energy waiting for hot water, as well as water supply and drainage piping.
19th century methods relied on windows, which had been disincentivized in the UK with the Window Tax, repealed in 1850.
November 23, 2025 at 5:31 AM
19th century methods relied on windows, which had been disincentivized in the UK with the Window Tax, repealed in 1850.
There’s so much you can do with air quality sensors. Hydrogen sulfide and ammonia sensors can be used as a proxy to know when public restroom maintenance is needed.
November 23, 2025 at 5:06 AM
There’s so much you can do with air quality sensors. Hydrogen sulfide and ammonia sensors can be used as a proxy to know when public restroom maintenance is needed.
ARUP’s Shanghai office has some really nice CO2 sensors scattered throughout with readings featured on a public display panel.
November 23, 2025 at 4:48 AM
ARUP’s Shanghai office has some really nice CO2 sensors scattered throughout with readings featured on a public display panel.
Ventilation was one of the original public health measures featured in early building codes in London and New York City. While contaminated water supplies were the real cause of cholera and typhoid outbreaks, airborne disease spread and high CO2 levels continue to plague modern buildings today.
November 23, 2025 at 2:49 AM
Ventilation was one of the original public health measures featured in early building codes in London and New York City. While contaminated water supplies were the real cause of cholera and typhoid outbreaks, airborne disease spread and high CO2 levels continue to plague modern buildings today.
“These vents for traps played a large, albeit, as experience has shown, pointless role in all countries for many years and are now considered completely obsolete (except in America and England.” -Otto Spiegelberg, 1916 in Gesundheit-Ingenieur
November 22, 2025 at 7:30 AM
“These vents for traps played a large, albeit, as experience has shown, pointless role in all countries for many years and are now considered completely obsolete (except in America and England.” -Otto Spiegelberg, 1916 in Gesundheit-Ingenieur
MIT’s 19th century single stack test rig. The German and Danish construction sector have benefited significantly from early American research in this area for well over 100 years yet most American plumbing engineers still aren’t familiar with the single stack today.
November 22, 2025 at 1:52 AM
MIT’s 19th century single stack test rig. The German and Danish construction sector have benefited significantly from early American research in this area for well over 100 years yet most American plumbing engineers still aren’t familiar with the single stack today.
“The committee has collected a large number of plumbing codes, State laws, and local ordinances and given them careful study. The situation may be described as chaotic.” 1929
November 21, 2025 at 11:00 PM
“The committee has collected a large number of plumbing codes, State laws, and local ordinances and given them careful study. The situation may be described as chaotic.” 1929
Ceiling-mounted horizontal piping is much more expensive to install (~2x compared to vertical) due to labor and additional piping supports needed. The above floor plumbing common in much of Europe also eliminates a lot of this piping as well.
November 21, 2025 at 8:41 PM
Ceiling-mounted horizontal piping is much more expensive to install (~2x compared to vertical) due to labor and additional piping supports needed. The above floor plumbing common in much of Europe also eliminates a lot of this piping as well.
Urinals do however enable efficiencies both in terms of cost, space allocation, and water usage. Providing separate restrooms designated with signage for WCs and another with signage for urinals, along with improvements to privacy to provide safer access to all, could offer an additional solution.
November 20, 2025 at 12:44 AM
Urinals do however enable efficiencies both in terms of cost, space allocation, and water usage. Providing separate restrooms designated with signage for WCs and another with signage for urinals, along with improvements to privacy to provide safer access to all, could offer an additional solution.
Some solutions focus on providing a separate single-user restroom (WC+lavatory) with no gender designation while others involve abandoning the urinal altogether and providing a common restroom with adequate privacy at WC stalls (something that is notoriously lacking in North America).
November 20, 2025 at 12:25 AM
Some solutions focus on providing a separate single-user restroom (WC+lavatory) with no gender designation while others involve abandoning the urinal altogether and providing a common restroom with adequate privacy at WC stalls (something that is notoriously lacking in North America).
Suburbanites viewing apartments as inescapable from the noise and pollution of cars is only reaffirmed the more construction is limited to single aspect units near busy roads.
November 19, 2025 at 4:23 PM
Suburbanites viewing apartments as inescapable from the noise and pollution of cars is only reaffirmed the more construction is limited to single aspect units near busy roads.
Robert Wyly and Herbert Eaton with NIST were aware of Wise’s work on the single stack at least as far back as 1961, and even cited his work in their reports, but not in the context of eliminating or simplifying requirements for vent piping.
November 17, 2025 at 10:01 PM
Robert Wyly and Herbert Eaton with NIST were aware of Wise’s work on the single stack at least as far back as 1961, and even cited his work in their reports, but not in the context of eliminating or simplifying requirements for vent piping.
NIST’s report, which is a review of existing literature on the single stack, came 2 years after Alan Wise with the BRS went on an educational tour in the US, visiting various cities and publishing articles for the American audience on the single stack.
November 17, 2025 at 9:49 PM
NIST’s report, which is a review of existing literature on the single stack, came 2 years after Alan Wise with the BRS went on an educational tour in the US, visiting various cities and publishing articles for the American audience on the single stack.
“But what is the use of a covered sewer through an alley which has not a single soil-pipe [the drain from WCs] into the sewer?”
November 17, 2025 at 6:49 AM
“But what is the use of a covered sewer through an alley which has not a single soil-pipe [the drain from WCs] into the sewer?”
The urbanism of Edinburgh in 1861
November 17, 2025 at 6:25 AM
The urbanism of Edinburgh in 1861
The single stack (Fig 105) was always the most obvious solution for drainage, but the dual concern over siphonage and cleaning miasma from drainage pipes (to prevent contamination of the water in the traps) resulted in a much more complex configuration with vent piping installed at traps (Fig 107).
November 12, 2025 at 2:15 AM
The single stack (Fig 105) was always the most obvious solution for drainage, but the dual concern over siphonage and cleaning miasma from drainage pipes (to prevent contamination of the water in the traps) resulted in a much more complex configuration with vent piping installed at traps (Fig 107).
All of the excitement over the ‘British single stack’ in the 1970s resulted in a slightly rivalrous memo drafted by an AHJ at the City of Philadelphia.
November 11, 2025 at 10:36 PM
All of the excitement over the ‘British single stack’ in the 1970s resulted in a slightly rivalrous memo drafted by an AHJ at the City of Philadelphia.
In his 1968 report on the single stack, Robert Wyly at NIST makes no mention of the single stack being used in Philadelphia or Boston. It’s unclear if Wyly was aware of this practice in the US Northeast.
November 11, 2025 at 10:29 PM
In his 1968 report on the single stack, Robert Wyly at NIST makes no mention of the single stack being used in Philadelphia or Boston. It’s unclear if Wyly was aware of this practice in the US Northeast.