Washing Machine Water Coming into Sink

The last ugly sight you want to see is water from the washing machine coming into your sink. It’s a dose of panic that homeowners deal with on occasion. No, it doesn’t always mean there’s something wrong with your pipes or the washing machine. It usually means there’s a blockage somewhere, and not just from the pipes either.

If your washing machine is backing up water into the sink, there’s three areas that are to blame: the waste line, dry vents, studor vents, or all three.

Fixing Washing Machine Water Coming into Sink

The best strategy right now is to not panic. Below you’ll find the necessary steps to take when dealing with any of the three possible causes of backed up water in your sink.

Unclog the waste line

First on your list is unclogging the waste line. Chances are a clog sewer line is exactly where the issue stems from. That may sound strange, but it’s possible that your washing machine, sink, and toilet all share a line at some point.

1. Start by plunging the nearest toilet. If there’s a blockage in the waste line, the toilet tends to be the closest to the clog.

Important: As a homeowner, realizing that you need to waste another Saturday waiting for the landlord or handyman to come over to fix another damaged appliance is frustrating. It shouldn't feel like the norm to constantly have damaged appliances and systems in your home since it can come to a huge cost at the end of each year.

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2. After you’ve tried the toilet, plunge the sink. Gross, yes, but necessary. In fact, for the sake of sanitation, buy a sink plunger (View on Amazon).

Investigate the vent opening

Like the waste line, your sink and washing machine might have their own dry vent that eventually meets with the main vent stack. If it gets blocked, it can and has caused others to experience washing machine water in their sink.

All you have to do is investigate the main dry vent opening. It should have any debris stuck in the opening. Nature is notorious for throwing sticks and leaves into the opening. After you’ve cleared it of everything, spray the dry vent opening with water. If the water doesn’t back up, then you’ve cleared the blockage.

Fix the studor vents

Studor vents are typically found in newer homes, a contraption that deals with air flow. Since the system relies on a spring-loaded valve, it can stick and stay closed. To fix it, simply unscrew the old one and replace it with a new valve. You can find the studor vent behind the washing machine.

Contact a plumber

After you’ve hit every single possible problem, and you came up short, it’s time to throw in the towel and bring in a plumber. If none of the above methods fixed the issue, then you have a problem with your pipes somewhere that a quick fix won’t help, nor a solution that is within your expertise. You have done all that you can.

Speaking of plumbers, start by checking in on local plumbers first. Since they’re generally closer to you, they’d be far more likely to show up at your house within the same day, sometimes the same hour. Sure, local businesses might have you pay a tad more than a corporation, but the jump gets done just as well—sometimes better—and during a window of time that works better for you rather than days from now.

Why Was Washing Machine Water Coming into the Sink?

When a washing machine and sinks are built near each other, chances are they’ll be sharing a drain. With that shared line, you could both the sink line and the washing machine line and find that, at some point, they become one. It’s a setup called “wet venting.” It’s nothing fancy, but since both lines eventually meet and empty into the toilet waste line, clogs are bound to happen.

While it’s nice that you don’t have a thousand and one different pipeline exits, when that single pipeline is clogged, it can cause problems for just about everything that shares the line. In this case, washing machine water could be coming into your sink, typically sinks that are the closest.

The problem is a domino effect. Since the toilet waste line is generally bigger to compensate for the other lines and increased air flow. Even a partial block is enough to create a blockage against that air flow, slowly but surely restricting that air flow as well as the water flow. Once both start slowing, the blockage gets bigger and bigger. Soon enough, the washing machine water is backing up into your sink. Gross!

Wet venting is only one possible answer, albeit the most likely. There’s the possibility that the dry vent opening is blocked or the studor vent is stuck—each having their own signature mark. If you spray water into a dry vent, and it comes back out, then you have a blockage. As for studor vents, it’s just an issue with design. Studor vents operate when negative pressure is introduced, and answers negative pressure with a spring-loaded valve, providing necessary increased air flow. Since it’s a spring, they’re almost guaranteed to break sometime down the line after being used so many times.

Preventing Future Clogs

It goes without saying, the best way to stop this from happening is to prevent it. That means changing any strange rituals or bad habits. Here’s a few tips you should take to heart, aside from keeping the studor vents and dry vents free of debris.

There’s a short list of products that you should never toss in your toilet such as:

  • Paper towels
  • Facial tissues
  • Feminine hygiene products
  • Extra-thick toilet paper
  • Wet wipes

Paper towels are designed to pick up spills and be far more resistant to breaking up than toilet paper. Facial tissues are made in a similar fashion and do not break up in water like toilet paper does. Feminine hygiene products should be a no-brainer. Wet wipes, even ones that specifically advertise as being “flushable,” actually aren’t flushable at all—and that’s coming from the mouths of plumbers. Extra-thick toilet paper sounds great, but once you step into 3-ply and 4-ply, you’ve gone too far. It’s too thick; 2-ply is all you need.

You Need to Know This About Your Washing Machine!

If you’re noticing problems with your washing machine, you need to know what’s causing the issue and if you’ll need to get the washing machine repaired or replaced. Having a working washing machine is crucial for any home, and fixing it is just one form of home improvement, but there are many more.

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Bottom Line

Halting the flow of washing machine water in your sink is a pretty straightforward affair. It has its roots in one of three possibilities or perhaps all three at the same time: waste line, dry vent, or studor vent. And thankfully, tackling any of those problems is relatively easy and can be done without the assistance of a plumber.

With that said, you should always consider calling a professional if you ever have second doubts. It’s much better to have a professional doing the job than you. In fact, if they screw it up, you’re not the one who has to pay for it. If you screw up, well, the problem is solely on your shoulders. Funny how that works. At any rate, you now know how to fix water coming into your sink from the washing machine as well as how to prevent it in the future.