Unplug the washer. Turn off the water supply valves. Move the washer away from the wall carefully (disconnect the drain hose from the standpipe first if needed). Have towels and a bucket ready for spills.
Straighten the hose and run a high-pressure stream of water through it using a garden hose or a bathtub faucet. If water doesn't flow through freely, the clog is inside the hose. 3. Snaking the Standpipe how to unclog washer drain pipe