A dishwaster has a hot water line connection and is classified as a “plumbing appliance." Plumbing appliances are required to have a shut-off valve. Here’s how it is stated at P2903.9.3 of the 2017 Residenital Edition of the Florida Building Code (FBC) and the International Residential Code (IRC).

    Earlier editions of the codes stated the same thing somewhat differently: “An individual shutoff valve shall be required on the fixture supply line to each plumbing fixture except bathtubs and showers.” The elimination of the word “individual” in the new code edition could possibly be interpreted by a local offical as meaning that a splitter shut off valve that serves supply lines to two fixtures—such as both the kitchen sink and dishwasher—is allowable. 

    “This type of thing will be taken both ways by different inspectors in different jurisdictions,” according to our plumber, James Freeman, of J.W. Freeman Plumbing. “The city inspector may see it one way and the county inspector another. If we were installing it, we would have a separate valve for each fixture."

    The codes further say that “fixture valves, when installed, shall be located either at the fixture or at the manifold” (P2903.8.5). A manifold is a central water distribution box, similar in concept to an electric panel, in that it has two rows of shut off valves, each of which connects to a pipe that goes directly to a specific plumbing fixture only. Plumbers call it a “home run” system, and we have only seen a manifold used with flexible PEX (cross-linked polyethylene) plastic pipe. 

    One of the peculiarities of a manifold water distribution system is that if, for example, you have two sinks in a master bathroom and turn on the hot water at one, then wait for a minute or so for it to arrive from the manifold, it will take the same amount of time again for the water to get hot at the adjacent sink. Conversely, one of the nice features of a manifold system is that it’s easy to have a shut off for every bathtub and shower.

   Also, the codes add that “if valves are installed at the manifold, they shall be labeled indicating the fixture served,” another similarity to an electric panel. The pipes are often color-coded blue for cold and red for hot water. Here’s a photo of PEX manifold system below.

   So, in summary, shut off valves are required for all plumbing fixtures and appliances, except showers and bathtubs, and they must be at the fixture unless a manifold system is used.

    See our blog post ”What is the difference between a plumbing fixture, a plumbing appliance, and a plumbing appurtenance?" for more on how the code categorizes different plumbing devices. For how long the valves will last, go to our article What is the average life expectancy of plumbing fixture water shut-off valves?

Because shut off valves sometimes fail by leaking very slowly at first, then gradually increasing, it’s important to check around them during a home inspection, especially where concealed—such as behind a refrigerator or washing machine.