2015 Uniform Plumbing Code meeting
Photo credit: ©istockphoto.com/Wisent


This spring, IAPMO starts the final round of meetings leading up to the publication of the 2015 Uniform Plumbing Code (UPC).

The meeting was recently moved from St. Louis to Las Vegas, but the dates remain the same (April 28-30). Those dates are coincidently the same dates as the International Code Council’s Green Code hearings in Memphis, Tenn.

Following the first set of meetings last year, it is clear that this edition of the UPC will look somewhat different. All plumbing standards will clearly be identified in the body of the code and there will be no more guessing as to which standard applies where and when.

At the upcoming meeting, the standards will be further clarified. Some of the proposed changes did not have the standards clearly articulated. Public comments to those changes will update the reference to the standard. Another problem with certain changes was that the standard was not published prior to the meeting. Many of those standards now are published and can be considered for adoption.

While standards impact the plumbing engineering community on a daily basis, perhaps the greater concerns are the proposed changes to plumbing systems. Some of the public comments that will be considered relate to sizing of water distribution systems, drainage systems, vent systems, medical gas systems and storm drainage systems. Basically, all the piping systems regulated in the plumbing code are up for consideration.

The water pipe-sizing requirements appear in the appendix. The procedures are a recommended method of sizing as opposed to a mandatory method. The proposed changes will update the fixture unit values and pipe velocities. Also added will be charts for sizing that have been taken from the ASPE Plumbing Engineering & Design Handbook of Tables. The sizing tables will be identified based on the piping material installed.


Drainage sizing

The drainage sizing requirements should generate the most discussion. There are proposals supported by many manufacturers to lower the drain size required for a shower. If approved, the minimum trap size would be 1 1/2 in.

Another change would add to the drainage sizing tables that are based on the work by Dr. Roy Hunter. The tables have been updated since Hunter, but they utilize the same principle for sizing. The UPC is the only remaining model plumbing code that does not use Hunter’s method as its main criteria of sizing a drainage system. Most of the resistance is based on the tables being new, despite actually being rather old. Since the UPC hasn’t used the tables, they probably are new to many of the members of the Plumbing Technical Committee.

Other drainage sizing proposed changes include removing the restriction on the number of water closets permitted on a 3-in. drain with the only limitation being the fixture-unit value. Similarly, the size of a kitchen drain is proposed to be lowered from 2 in. to 1 1/2 in. Currently, the UPC allows a 1 1/2-in. trap for a kitchen sink, but requires the drain to be increased to 2 in.


Venting changes

In the venting section, there are public comments involving wet venting, circuit venting and air-admittance valves. There also is a change proposed regarding the sizing of vent stacks.

The committee accepted a change to the wet venting section that inadvertently removed the double bathroom group wet vent. That needs to be corrected. They also have added provisions that are different from the other plumbing codes. The public comment would also correct this.

Circuit venting has been an issue of whether the system is an engineered design or a plumbing system. I know that seems kind of crazy, but it relates to how the system is approved or accepted by the local authority. If the requirements appear in Chapter 9 of the code, anyone can design a system using a circuit vent. By being in the appendix, as the requirements currently are, a local official can refuse to accept the design. Technically, the local officials shouldn’t be able to do that, but the way the code is written allows for it. Hence, ASPE has submitted a public comment to move circuit venting from the appendix to Chapter 9.

What would venting be at IAPMO without discussion of air-admittance valves? Interestingly, no manufacturers of air-admittance valves are involved in the public comment. The comment was submitted by ASPE to accept air-admittance valves and ASPE is identifying the use of these valves as another method of venting a drainage system.

The committee accepted a change for medical gas systems that utilizes the medical gas sizing tables as published by ASPE. However, with the new tables in place, some of the wording on how to size the system must be corrected. A public comment will add language similar to what ASPE has in their Engineering & Design Handbook.


Down the drain

Discussion of storm-drainage sizing should be the most fun at the meeting. ASPE submitted a change to update the storm-drainage sizing based on the ASPE Research Foundation report. The Plumbing and Drainage Institute did not care for this proposal, so it submitted a change requiring storm drainage to be based on a maximum of 2 in. of ponding at the roof drain.

What the PDI change doesn’t tell an engineer is how to calculate for 2 in. of ponding. As every engineer knows, you first need to know how much water is going down a particular roof drain to determine when the ponding will hit 2 in.

The ASPE proposal will require the roof drain flow rate to be used in sizing. This has created concern with some manufacturers because they are not crazy about publishing flow rates for each of their drains.

The sizing method proposed to the UPC already has been accepted for publication in the 2015 International Plumbing Code. It should be noted that ASPE and IAPMO are jointly developing a test standard for determining the flow rate through each roof drain.

You can download and review all public comments submitted here. If you want to speak out for or against any public comment make sure to be in Las Vegas the last week of April. I’ll see you there.