Technical Committee recommends acceptance of air admittance valves and non-water supplied urinals for the first time.

The third round of the International Association of Plumbing and Mechanical Officials Plumbing Code change cycle took place the first week of May in Denver. The IAPMO Plumbing Technical Committee (TC) reviewed the comments submitted by the public following their recommendations last year. The comment period also included the vote taken by the membership at the IAPMO Convention last September in Las Vegas.

During this code change hearing, the hot issues were reviewed in further detail. This is also the hearing that allows proponents to correct original code changes with modifications or revisions.

First Up, AAVs

What better way to start off the code hearing than with air admittance valves? You may recall that the IAPMO Plumbing TC recommended the acceptance of air admittance valves under an engineered design. The requirements would appear in the appendix of the Uniform Plumbing Code, not the body of the code.

Even though the use of an air admittance valve would require a licensed professional engineer to design the system, certain segments of the IAPMO membership were still adamantly opposed to any mention of the words “air admittance valve” in the UPC. Those testifying against air admittance valves were unaware that air admittance valves are already mentioned in the code, in Appendix L under the engineered design of single stack vent systems.

For the first two hours, the committee heard all of the reasons why air admittance valves should not be considered for engineered designs. The supporting data, submitted in opposition to air admittance valves, was poor, at best. It included inaccurate data from a test project, as well as biased tests where the valves were placed in failure mode.

At the same time members were opposing air admittance valves, one of the manufacturers was trying to add air admittance valves to the body of the code. The manufacturer argued against requiring the system to be an engineered design.

After all of the discussion, the TC voted to confirm their original vote to add air admittance valves to the appendix as an engineered design option.

The other subject that received considerable attention was non-water supplied urinals. The public comments to reject the acceptance of the urinals were swiftly rejected. The TC voted to maintain the acceptance of non-water supplied urinals.

While the urinals were accepted, a comment submitted by myself to add a fixture unit value for non-water supplied urinals received the bulk of the debate. Sometimes simple changes to help correlate the code are not so simple. This was one of them.

My intentions were innocent enough in that, once the code recognizes non-water supplied urinals, there should be a corresponding listing in the fixture unit table identifying the fixture unit value and the minimum trap size. The comment was viewed by many as much more than that. Those opposed to the change saw the comment as a means of really accepting non-water supplied urinals. Up until that point, they viewed the acceptance as a temporary measure to make the “greenies” happy. Then, within months of the installation, they expect them to be replaced with water-supplied urinals.

The supporting comments that non-water supplied urinals did not have the same impact on the overall drainage system as water supplied urinals didn’t seem to matter. In the end, the TC rejected the comment, leaving the code without a fixture unit value for non-water supplied urinals.

Mean and Green

One of the important “green” code changes related to maximum flow rate permitted from a shower valve. Some manufacturers have incorrectly interpreted the federal requirement on water conservation as applying to each shower head. Hence, they have been promoting multiple shower heads.

The public comment modified the proposed change to indicate that each shower is entitled to 2-1/2 gpm, whether through one shower head or multiple shower heads. The change established the size associated with each shower. Thus, it would still permit a two-person shower with two shower valves if the shower compartment is large enough.

The IAPMO Green Committee representative read a statement indicating the importance of the Uniform Plumbing Code being a green document. The arguments against this change all sounded either greedy, not concerned about water conservation, or interested in selling multiple shower heads. The TC voted to approve the comment limiting each shower to a maximum flow rate of 2-1/2 gpm.

Other important green changes were to the reclaimed water chapter of the code. All of the changes to this chapter were previously rejected and sent to an Ad-Hoc Committee. The Ad-Hoc Committee revised all of the changes to the reclaimed water section.

Some of the more important aspects of the comments from the Ad-Hoc Committee included allowing the use of reclaimed water in all buildings. The current code restricts the use in residential buildings. In addition, reclaimed water can be either publicly supplied or supplied by an on-site system that uses gray water or harvests rain water.

There was little fanfare as the TC accepted all of the comments from the Ad-Hoc Committee on reclaimed water. Two minor editorial modifications were made to the labeling of the system.

More On Grease

Another Ad-Hoc Committee submitted comments on the sizing of grease interceptors. This Ad-Hoc Committee proposed to reverse the advances made on sizing. Rather than use the sizing by flow rate through the interceptor, the Ad-Hoc Committee proposed using drainage fixture units.

Leading experts in the area of grease interceptor design pointed out that the interceptors must be sized by flow rate. They pointed out the potential undersizing that could result by using fixture units.

I could not resist adding a comment that sizing grease interceptors by fixture unit values is a recipe for disaster. Many failures have resulted when the design professional did not take into account the peak demand flow into the interceptor during heavy use by a food-handling establishment.

The TC rejected the comments from the Ad-Hoc Committee and reaffirmed their support for sizing by flow rates.

The results of the IAPMO hearing will be published in a Report of Comments that should be available on-line within the next month at The IAPMO membership will have one remaining opportunity to review the changes and encourage the TC to modify a submittal. That meeting will take place in conjunction with ISH North America in Atlanta the last week of September.