Interpretation #9536

Original Request

Code Version: 2023
Code: RESIDENT
Code Description
Chapter: 29
Section: P2903.5
Topic: Hammer arrestors

Question

Regarding hammer arrestors or specifically hammering of pipes. There are different interpretations of this code among several Jurisdictions. Water hammer arrestors are to be installed where quick closing valves are used by mechanical, automatic or manual means. A single lever faucet or even some single lever mixing valves shut quickly and cause hammer in piping. So, the question is if a single lever faucet or mixing valve is considered to be a quick closing valve and would require a hammer arrestor?

Answer Published 05/23/2026 at 8:00 AM

No, a standard single-lever faucet or manual mixing valve is not considered a quick-closing (or fast-acting) valve in the plumbing industry. Further, the definition of a QUICK-CLOSING VALVE is a valve or faucet that closes automatically when released manually or that is controlled by a mechanical means for fast-action closing. Therefore, unless the faucet releases quickly after the manual movement to open the faucet has been removed, it is not a quick closing valve.

Commentary

According to the IRC Commentary, the code defines a quick-closing valve as any type of solenoid-actuated valve, spring-loaded, self-closing faucets; or any other device capable of instantaneously reducing water flow from a full-flow to a no-flow condition. Although most faucets can be manually closed fast enough to produce water hammer, the code does not designate manually closed valves or faucets as "quick-closing."