What Causes a Washing Machine's Drainage to Backfeed Into the Toilet?

Blockages

• Check other fixtures in your home to ensure that they’re draining correctly. If the only problem you have is with water draining from the washing machine, a blockage or vent problem might exist at that fixture. If other fixtures also are giving you problems, the problem might be with your septic system or main sewer line.

Clearing Drain

• Washing machine drain clogs are usually tough and consist of large amounts of lint, soap scum and sand. An electric power auger may be needed to clear it out. Rent an auger with at least 50 feet of cable and a foot-pedal switch, which leaves your hands free to snake the cable. The cable can be fed straight down the pipe by removing the clean-out plug, or you can feed it through the trap. When you’re through, don’t forget to replace the clean-out plug or dangerous sewer gases could enter your house.

Waste Vent

• If the drain isn’t blocked, you should check the plumbing vent on the roof in case an animal or insect nest is blocking it. Snow and ice also can cause blockages in winter. Although vent blockages are more likely to cause slow draining than backups, it’s worth investigating, especially if you also hear a gurgling sound when the water drains from the washing machine.

Septic System

• If the washing machine drain isn’t blocked and the vents are also free from blockages, you may have a blocked or damaged drain line between your house and septic tank. Use a snake to clean the drain line. A professional drain cleaner may be able to tell what kind of problem you have just by the way the snake feels. You may need to open the septic tank and check the intake and outlet drains for blockages, and check the distribution box to see if the outlets are distributing effluent equally.

Sewer Line

• If you don’t have a private septic system and there is no blockage in your home system, you could have a blockage in the sewer line between your house and the sewer main. Call your local water department. Property owners are responsible for repairing problems in the sewer line between their home and the public sewer main, but you may need permission from your municipality before you can begin work.