Earlier this year, I received an announcement to go to the ICC website and read the Plumbing Code Economic Impact Report. I would encourage all of you to do the same. The website is: www.iccsafe.org

Without looking, I knew the report would be a cost comparison between the ICC International Plumbing Code (IPC) and the IAPMO Uniform Plumbing Code (UPC). As expected, the report showed how much of a cost savings there is for the installation of plumbing systems when you follow the IPC, compared with the higher cost for the UPC. 

The presentation of the report is very flashy and well done. As an engineer, I was more interested in the actual contents of the report. How are they coming up with these numbers? Is the cost savings real?

What catches your eye is the executive summary that lists the overall cost savings on a national level if the IPC is used rather than the UPC. Over a 12-year period, they list a cost savings of $38 billion. Then it lists 1 million tons of CO2 release saved. Now I was really curious as to where these numbers originate.

It took some searching, but I finally found the link to the report’s Technical Appendix. The Appendix is 337 pages in length. Apparently, the report is the executive summary with this huge appendix.


A look at the details

The buildings that were studied were a(n): single-family dwelling, apartment, elementary school, grocery store, hotel and office building. The size of the buildings were somewhat strange. For example, the single-family dwelling selected had 4,500 square feet. I thought I lived in a large house and I only have 3,600 square feet, almost double the size of my last house. It seemed like a rather large house for comparison purposes.

When I looked at the design of the various plumbing systems, I was surprised that ICC would allow them to be printed. There were a number of plumbing code violations shown on the DWV risers. There were lavatories installed with “S” traps, something not permitted in either code. There were flat vents; again, not permitted in either code. There were kitchen sinks discharging into wet vents. Many of the pipe sizes were not the minimum size permitted by the code.

In order to reduce the amount of DWV piping under the IPC, they provided air admittance valves (AAV) for almost all of the venting circuits. They did not show one AAV under the UPC. The interesting aspect of that design feature is that the UPC will allow an AAV under engineered design found in Section 912. 

Even when the design used AAVs, the AAVs were in a more expensive location. I would have placed the AAVs under the sink or lavatory, where there is ready access and a savings in the amount of piping required. They had the AAVs in the wall, which would require an access door, however, they did not include the cost of an access door in the plumbing estimate.

For the commercial DWV design, they didn’t select the least expensive piping installation for either code. I would have been using a circuit vented installation for many of the fixtures to keep the cost down. Both the IPC and UPC allow circuit venting. So, the cost savings using IPC would not be found.

For the most part, the water piping design should have been the same for almost every building, using either code. The exception would be apartment buildings. Otherwise, both codes allow the same water piping materials and both codes allow an engineered design. Although both the IPC and UPC have a water pipe sizing method that can be used and neither method is great. The better sizing method is found in the National Standard Plumbing Code. The 2021 UPC, which will be published shortly, also has a better sizing method for residential buildings.

Bias in the analysis

The apartment building had a horizontal water piping design, something I would not have selected to achieve the lowest cost. However, this worked out in favor of the IPC, since the code requires an individual shutoff for each unit. If vertical piping was installed, as allowed in the UPC (without the need for an individual shutoff valve to isolate each unit’s water piping), the cost of the water piping would have been significantly less. However, for the UPC design, they also showed a horizontal piping layout. That is not a good comparison and it shows bias in the analysis.

The problem with coming up with outrageous numbers such as $38 billion in savings is that it assumes every engineer is going to design plumbing systems based on the design the firm who prepared the study used. Not every engineering firm is going to choose their design. As I identified, I would have done very different designs, many of which would be lower costs under both codes. 

Similarly, many engineers do not design to the minimum allowed by code. They may select other designs that they believe are better. For example, I personally am not a fan of combination waste and vent systems. I’ve designed systems using combination waste and vent, however, I avoid using such a system as much as I can. Just a personal preference. Yet, I will defend anyone’s right to use a combination waste and vent system.

When you look at the nuts and bolts that came up with $38 billion in savings, and 1 million tons of CO2 release saved, you realize that such numbers will and could never occur. This is a pipe dream in someone’s imagination.

As I have always stated, code comparisons will depend on who is doing the plumbing design and what contractor is doing the construction estimate. If that was not the case, we wouldn’t have plumbing project estimates that are all over the place. Think of your last project and the variation in estimates between the various contractors. If we are going to save $38 billion, every estimate better be the same and they better be low. 

It is unrealistic to think you can save $38 billion over 12 years by using a certain plumbing code. While I appreciate the concern for cost, and I always think about that when dealing in the codes and standards profession, isn’t the most important aspect of any plumbing code the protection of public health and safety? We cannot always put a cost savings above the protection of public health and safety.