On April 1, IAPMO issued its code change monograph for the 2024 Uniform Plumbing Code and 2024 Uniform Mechanical Code. This begins the two year cycle of reviewing proposed changes.

The technical committee meetings for both codes will be held virtually the first and third week of May. Anyone can sign up to observe the meeting and discussion of code changes. In order to testify, individuals must register with IAPMO staff at least a week before the meeting. Individuals not registered to testify will not be granted the opportunity to speak during the virtual meetings.

There were 347 changes proposed to the Uniform Plumbing Code, and 349 code changes proposed to the Uniform Mechanical Code. While the numbers seem high, they are actually consistent with previous code change cycles.


Proposed changes

There were some code changes that appear shocking for the Uniform Plumbing Code. ASSE submitted a proposed code change to allow the use of air admittance valves. ASSE, which is now a part of IAPMO, promulgates the three air admittance valve standards. The first attempt to gain approval of the use of air admittance valve in the Uniform Plumbing Code was more than 30 years ago. The code changes have continually been rejected. With more than 33 years of use in the United States, there is a possibility that air admittance valves may be accepted, especially when the code change is coming from ASSE.

Some will also be shocked by the number of proposed changes regarding the reopening of buildings. IAPMO had a committee, on which I had the honor to serve as a member, which developed a new document on the closing and opening of buildings in light of the COVID-19 pandemic. Sections from the new document are being proposed to the appendix of the Plumbing Code. The code changes are quite good, with input from all segments of the plumbing and water quality industry.

ASPE proposed a change to move the single stack drainage and vent system from the engineered plumbing appendix to the body of the code. It has been common practice at IAPMO to have systems new to IAPMO first added to the appendix, then a few years later, the text is moved from the appendix into the body of the code. The single stack system is what is also known as the “Philadelphia Single Stack.” The requirements were first developed by the Plumber’s Union in Philadelphia.

Both the Plumbing Code and Mechanical Code have changes regarding Legionella. All of the code changes appear under my name since I had the privilege of chairing the IAPMO Legionella Task Group. The 2021 Uniform Plumbing Code added an appendix of Legionella. The proposed changes to the Plumbing Code will add specific code requirements to the body of the code, as well as, update the appendix.

One of the main emphasis of the Legionella Task Group was related to code requirements for cooling towers. These proposed changes appear in the Mechanical Code monograph. The major changes to the Mechanical Code is the addition of a new appendix, similar to the Plumbing Code appendix. However, unlike the Plumbing Code, there are measures for testing and treating systems based on Legionella concentration.

If accepted, new to both codes will be a thermometer pictograph identifying the Legionella growth potential at various temperature ranges. Watts Water Technology was kind enough to allow the Task Group and IAPMO to use the thermometer pictograph they developed. The pictograph provides readily visible information regarding Legionella.

What would an IAPMO code change cycle be without a number of changes to the wet venting and circuit venting sections? This cycle, the changes to the circuit venting section would extend circuit venting to any horizontal battery of fixtures. One change proposes to allow wall hung or back outlet water closets to be circuit vented. Another change would allow for circuit venting of any battery of fixtures connecting horizontally. The current code restricts circuit venting to floor outlet fixtures only. I have always been of the opinion that the pipe doesn’t know if it is above the floor or below the floor when being vented. Others have disagreed.

A rather simple code change would increase the minimum vent frost closure size from 2 inch to 3 inch. The Uniform Plumbing Code has been the only code where 3 inch was not the minimum size for preventing frost closure. However, in defense of the code, it is also the only code that allows the vent to terminate at a lower height above the roof, thus assisting the prevention of frost.

With the addition of tall wood buildings, there is a proposed change to address plumbing systems in such buildings. However, the code change appears to be an attempt to limit the use of plastic pipe and plastic plumbing fixtures. It would require plumbing systems to have a flame spread index of 25 or less and a smoke developed index of 50 or less. There is also a requirement regarding expansion, contraction, and differential movement. The only justification given for the flame spread and smoke developed requirement is that tall wood buildings are two- or three-hour fire-resistance rated. So what? I could see this code change taking us back to the dark ages of not allowing any plastic pipe or plastic plumbing fixtures in buildings of Type 1 or Type 2 construction.

As with all code change cycles, there are numerous code changes to update standards, add new standards, and add new piping material. There are also many changes that are editorial in nature.

The IAPMO monographs can be downloaded from the IAPMO website, IAPMO.org. You can also register to view the code hearing on the IAPMO website. In order to testify, a request must be emailed to the staff engineer responsible for the given code.

At the current time, the code change meetings are scheduled to run each day from 8 a.m. to 12 p.m. PDT. Those times can be adjusted by the chair of the Technical Committee, depending on the speed of reviewing the code change. I would encourage everyone to register to view the code change meetings. They are very educational. With them being virtual, you have the opportunity to participate without having to travel.


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The views expressed here are strictly those of the author and do not necessarily represent PM Engineer or BNP Media.