Why is my washing machine drain overflowing?

A washing machine standpipe can overflow when water leaves the washer faster than the drain can carry it away. Buildup in a nearby trap, a partially blocked branch drain or an improperly arranged standpipe are possible causes. Stop the wash cycle, avoid running more water into the drain and clean up standing water only if there is no electrical hazard. Check whether nearby sinks or tubs are also draining slowly; that detail helps show how far the blockage may extend. Do not force a hose into a sealed drain opening or rely on harsh chemicals. A plumber can assess the drain and whether its arrangement suits the washer.