Laundry Drain Backing Up or Overflowing?


The house drainage system is a comprehensive pipe system with many connections and specific uses. You might find a washing machine linked to the basement drainage or w dishwasher to a sink drain. It could be possible that the laundry room is near the kitchen, which will mean that the two will share the same drainage. Because of this drain blockages and clogs often impact the whole drain system.

Why Does a Laundry Back Up?

A laundry backup will occur if the drainage has been blocked, and hence, water cannot move through the outlet, into the waste line. For that, the water will accumulate in the drainage system, and there might be an overflow inside the laundry room from the water outlet. Alternatively, the water could climb back to the sink, if the laundry drain has been linked with the kitchen drain. As a result, the water will pile up, and it might have a foul smell.

The color of the water from the drainage will also not be pleasant, because all the dirt along the drain will be pushed back into the laundry room, or the kitchen sink. So in case you realize an overflow in the laundry room, then most likely, the drain is clogged, which blocks water from flowing. The backup will mostly happen when the washing machine is draining the water into the drains.

What Causes The Back Up?

There are a number of causes that could lead to the laundry back up, however, here are some common reasons that will make the water overflow back into the laundry room:

  • Tiny Waste Lines. In most cases, the laundry drain will be connected to the toilet waste line, which receives all the water pumped by the washing machine. If the waste line is tiny, air might be blocked from flowing freely through the pipes.
  • Solid materials from the toilet. Since most of the laundry drains will be connected to the waste line of the toilet, a major backup could be caused. Suppose there are some solid materials like sanitary napkins along the toilet drain, the entire system will be clogged. Since water cannot flow through the waste line, it will gradually climb back into the laundry drains.
  • Main Stack Blockage. Some laundry drains will be connected directly to the main stack, differently with the kitchen drains. In these cases, there could be a possibility that the main drainage is clogged. You could realize this if there is a water overflow around the drainage. Debris like sticks, leaves, tree roots or other stuff could be stuck in the drainage system, which will in turn affect the laundry system.
  • The type of vent. Suppose you have just installed a new washing machine in your house, it could be fitted in with a new vent, called the Studor Vent. This vent will not allow you to run new vent pipes via the walls. As a result, there would be a negative pressure that will open a valve that has a spring, which lets air to flow freely. The valve could stick, which will then cause water not to flow.


It is always advised to ensure that the toilet has no sanitary napkins, and other solid material flushed, if the laundry drain is connected to the toilet waste line. All in all, it is important to contact a professional plumber to check and fix any possible problem.