The short answer
An isolation valve kit is a pair of valves, one on the cold inlet and one on the hot outlet, each with a shut-off and a purge (hose) port. They let you flush the heater without cutting pipe, and the hot-side valve usually has a port for the pressure relief valve plumbing codes require on a water heater. Match the connection (threaded, sweat or push-fit) and the pipe size, usually 3/4 inch, to your plumbing.
Kits in the catalog
BRIGHTDECK A01 3/4" Tankless Isolation Valve Kit, CMI 3005IPS Tankless Isolation Valve Kit and Camplux VK75 Tankless Isolation Valve Kit.
Fitting notes
- Threaded (IPS) kits screw onto the heater's fittings.
- Sweat kits are soldered into copper lines.
- Push-fit kits connect without solder; check the pipe types they accept.
Products mentioned
Isolation valve kit · BRIGHTDECK
BRIGHTDECK A01 3/4" Tankless Isolation Valve Kit
Isolation valve kit · most American residential tank
Isolation valve kit · CMI
CMI 3005IPS Tankless Isolation Valve Kit
Isolation valve kit
Isolation valve kit · Camplux
Camplux VK75 Tankless Isolation Valve Kit
Isolation valve kit
Questions readers ask
Do I need isolation valves on a tankless water heater?
They aren't the heater itself, but makers' flushing procedures assume them, and the hot-side port is a common place for the relief valve.