Amendments made to the Uniform Plumbing Code


The International Association of Plumbing and Mechanical Officials (IAPMO) has made a tentative interim amendment to the 2021 edition of the Uniform Plumbing Code and is asking the public for comment. The deadline to submit comments is Dec. 2.

Changes are being made to the  “backflow prevention devices, assemblies and methods “ section of the code—specifically  “Table 603.2. “ The proposed change will be to remove  “no valve downstream “ from the installation subsection and replace it with  “have outlet open to atmosphere.”

“The 2021 UPC has a conflict regarding the installation requirements for atmospheric vacuum breakers (AVB). Table 603.2 states that there shall be “no valve downstream.” However, ASSE 1001 was updated in 2017 to remove the wording “no valve downstream” and add, “have its outlet open to atmosphere.” Table 1701.1 in the 2021 UPC for Reference Standards includes the 2017 edition of ASSE 1001. Therefore, the installation requirements for atmospheric vacuum breakers in Table 603.2 must be updated as shown above to correct this conflict with the 2017 edition of ASSE 1001. Allowing a valve downstream from an AVB that does not create backpressure on the device is not a public health hazard,” according to the tentative interim amendment document.

A valve in the outlet to the AVB would create backpressure if it were considered a control valve and completely stopped the flow of water exiting the AVB. But, if the valve is not a shutoff or control valve and is located in a branch of a TEE that does not block the outlet of the AVB to the atmosphere, the requirement has been met.

By prohibiting all downstream valves, it restricts the design and doesn’t represent current certified designs that meet the intent of the code.

The reason why this change has been suggested now is partially due to the challenges this creates for manufacturers and end-users. According to the proposal, many commercial dishwashing machines have an auxiliary valve downstream of an AVB. The valve is located in a branch of a TEE that can’t prevent the AVB from being open to the atmosphere. Since it doesn’t meet the literal interpretation of the wording of the table, some AHJs have required customers to replace the AVB with an RPZ or spill resistant pressure vacuum breaker. Citations for those found in non-conformance are delays in receiving the final CO, modification fees from $1,200 to $2,000 per site, loss of manufacturer warranty, and voiding third-party sanitation certification.

Another reason for the proposal is because of the loss of NSF certification. “When an NSF certified commercial dishwashing machine is modified to replace the AVB with an untested device, that NSF certification is rendered null and void. As such, the customer is susceptible to a possible public health citation for using a non-certified dish machine. An even more significant ramification is a possible reduction in the sanitizing efficacy of the dish machine which is a potential public health concern.”

The initial requirement was included to prevent the VB from being subjected to constant working pressure from the water supply by closing a valve. With no downstream manual or mechanical valve to prevent the water pressure from dissipating after the operation of the rinse cycle, the AVB would be sufficient backflow protection, reports Bruce Pfeiffer, chair of UPC Answers and Analysis Committee.

The initial tentative interim amendment was submitted by Joel Hipp, agency approval engineer at Hobart.

Completed forms for the UPC can be emailed to Enrique Gonzalez, plumbing code development administrator, at


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