What is the purpose of a fixture isolation valve, and when should it be used?

• A. It filters sediment from the supply; installed on the fixture’s supply line near the main.
• B. Allows maintenance on a fixture without shutting down the entire system; installed on the fixture’s supply line or branch.
• C. It regulates pressure to every fixture; installed on the main supply.
• D. It reduces water hammer in the system; installed on the main.

Answer: (B)

A fixture isolation valve is designed to shut off water to a single fixture so you can perform maintenance or repairs without interrupting the rest of the system. It’s placed on the fixture’s supply line or branch, right at or near the fixture, so you can isolate that fixture while the other outlets keep working.

This is especially useful when replacing a faucet, addressing a leak, or swapping out a valve under a sink. You close the valve, drain the small section if needed, and work on the fixture without shutting down water to the whole house.

It’s not meant for filtering sediment, regulating pressure for every fixture, or reducing water hammer. Those tasks are handled by separate components, such as filters, pressure-regulating devices, and water hammer arrestors, respectively.