Why Does My Sink Back Up When I Run the Washing Machine?

Posted Apr 5, 2017

Every now and then something strange happens that is simultaneously baffling and frustrating. Gray water from your washing machine backing up into your sink is one such problem and for many homeowners it can be an ongoing source of annoyance.

Why does this happen?
To start with, know that your sink and washing machine drain lines tend to run congruent to each other. This means they combine at some point on the way to the main sewer line. So, if there is a problem after they combine, it can affect both systems.

How to Fix the Problem
First, you must pinpoint the problem. More often than not, a washing machine backup will occur in one or more sinks during or after the drain cycle of your washing machine. This may not happen every time or it may get progressively worse. It depends on why it is happening in the first place.

If the sink doesn’t back up on its own when you do the dishes or run the faucet, the clog is probably deeper in the pipes and only responds to the large volume of water being drained from your washing machine. In either case, you probably have a clog in the drainage pipe after the two combine.

Do NOT use any chemicals to clear the clog. Not only do chemicals cause damage to your pipes, which can lead to cracks and leaks later, they are not always effective at actually removing the problem – they simply minimize it in the short term.

To solve the problem, you’ll either need to plunge the sink and hopefully clear out the clog or have someone snake the line to pull the clog out of the drain pipe. If you cannot clear it on your own, it may be a good time to call a Milani plumber for a more in-depth attempt to fix the problem.

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