What Size Pipe Is Needed for a Washing Machine?

A washing machine is connected to a drain hose and to hoses that connect to the hot and cold water supply. The drain hose is connected to a stand pipe attached to the water drainpipe. Although the pipe sizes are generally standard, each jurisdiction's building and plumbing codes could have specific requirements for the size of the pipes and how the washing machine's drain system is installed.

Woman doing laundry
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The pipes and hoses are behind the washing machine.

Stand Pipe

The stand pipe, which taps into the water supply drain line, should be 2 inches in diameter. The stand pipe sits on a P-trap on the drain system. The top of the stand pipe should be higher than the washer's water level, which is generally 18 to 30 inches high. The height of the stand pipe and the P-trap prevents water overflow when the washer is draining.

Drain Hose

The drain hose, which drains the water out of the washer, can be connected to an existing laundry sink or into the stand pipe. The drain hose is available in different lengths, and universal sizes are 1 to 1¼ inches in diameter. The length of the drain hose depends on how far the washer is from the stand pipe or laundry sink.

Hot and Cold Hoses

Two standard hoses are connected from the back of the washing machine to the water supply valves. The hot and cold hoses are ¾ inches in diameter. The hoses typically are marked to distinguish them from each other. Some hoses are constructed to be used for both hot and cold water.

Installing

Installing the pipe and hoses is an easy process. First, connect the stand pipe to the water's drain line. Screw in the hot and cold hoses to each designated connection on the back of the washing machine. Connect the hot and cold hoses to the hot and cold water supply lines. Connecting the hot and cold hoses sometimes requires using water-pump pliers to a secure connection. Attach the drain hose to the washer, and insert the other end of the hose into the stand pipe or sink. A standard drain hose comes with a clamp to secure it in place. Push the washer into place and level it by adjusting the feet underneath it and using a level tool.