Written by IAPMO 6:15 pm Answers and Analysis Q&A

Answers & Analysis | Second Quarter 2023

Taken from the Online Editions of the UPC & UMC Answers & Analysis

SUBJECT: Drainage Pan SECTION: 507.5 (2021 UPC) 


Does an on-demand water heater with approx. 2-gallon capacity, installed in a cabinet, under a kitchen sink, require a drip/drainage pan to be installed under it? 


The location of the cabinet determines if a pan would be required. Section 507.5 of the 2015 Uniform Plumbing Code states that “where a water heater is located in an attic, in or on an attic- ceiling assembly, floor-ceiling assembly, or floor- subfloor assembly where damage results from a leaking water heater, a watertight pan of corrosion-resistant materials shall be installed beneath the water heater.” All water heaters, regardless of type, installed in a cabinet that is constructed on an attic-ceiling, floor-ceiling or floor-subfloor assembly would be required to have a pan. 

SUBJECT: Seismic Provisions 

SECTION: 507.2 (2021 UPC) 


Are anchor and strapping requirements mandatory for all water heater installations, regardless of the state or geographic region? 

Comment: Seismic categories C, D, E and F have been removed, makes anchor and strapping requirements mandatory for all installations.


Yes. Per Section 507.2 of the 2021 Uniform Plumbing Code (UPC), “water heaters shall be anchored or strapped to resist horizontal displacement due to earthquake motion.” The seismic location provision found in earlier codes has been removed. 

Note: The Technical Committee and IAPMO membership approved this code change with the following substantiation submitted by the proponent: “There have been fire and property damage due to falling or moving water heaters. Where earthquake motion moves a water heater there are times when heaters do not fall over, however, the connectors are sometimes ripped off. This proposed code change removes the specific seismic design categories and makes the anchor and strapping requirements mandatory for all installations. One cannot predict where and when an earthquake or other force of nature will move the ground, and create possible dangers with water heaters that are not secure.” 

SUBJECT: Accessibility for Service 

SECTION: 507.26 (2021 UPC) 


Does Section 507.26 require a permanent ladder to be provided to reach a lowboy electric water heater installed 6 feet above the floor? 


No. The 2000 Uniform Plumbing Code was the last code that required a permanent ladder for water heaters installed on platforms eight (8) or more feet above floor level. Section 507.26 of the 2021 Uniform Plumbing Code requires accessibility for maintaining and services appliances, but does not address permanent ladders for water heaters installed on platforms above floor level. 

SUBJECT: Environmental Air Ducts 

SECTION: 502.2.1 (2021 UMC) 


1. What is the minimum height above a public walkway that an environmental duct can discharge assuming horizontal discharge direction? 

2. Would an environmental exhaust louver placed 10 feet or greater above the walkway be considered compliant within the intent of the code? 


1. Section 502.2.1 of the 2018 Uniform Mechanical Code, prohibits environmental exhaust ducts discharge onto a public walkway. 

2. No, as this would not meet the requirement of not discharging onto a public walkway. 

SUBJECT: Condensing Dryers 

SECTION: 504.4 (2021 UMC) 


Are condensing dryers covered under section 504.4 of the 2018 UMC


Condensing Dryers are not under the scope of §504.4 of the 2018 Uniform Mechanical Code. They are covered under the provisions of §504.1 exception 2. “Condensing clothes dryers where installed in accordance with the manufacturer’s installation instructions.” 

Last modified: May 8, 2024