Why Does My Kitchen Sink Gurgle When My Washing Machine Drains?

There’s a load of laundry in your washing machine, the first spinning has just finished, and it is draining the drum to prepare for the rinse.   The washing machine is in the room adjacent to your kitchen, and as it begins to drain, there’s a bit of gurgling coming from the kitchen sink.

Why, you wonder?  And, is that bad? 

A Gurgling Sink When the Washer Drains Tells a Story

It is not uncommon for a washing machine to share drain lines with a sink.  If your laundry room is adjacent to your kitchen, the drain pipe is likely shared with its sink.  Plumbing your house this way cuts down on the cost of piping and labor. 

But, if your kitchen sink gurgles when the machine drains, or worse, your sink fills up with water, that is a problem. 

When the washer drains, either after the wash or the rinse cycle, it pushes the water out at a high volume using a drain pump. When that gurgling noise appears in your sink, it will usually suggest the drain lines shared by the machine and the sink is blocked to one degree or another. 

The blockage is preventing the water from being pumped out fast enough.  So, it gurgles. 

Or, the venting system is partially obstructed.  Your plumbing system includes a venting pipe that runs up the house and through the roof.  This allows air into the pipes so that water can flow through them smoothly.

All plumbing fixtures, including washing machines, must be vented.  If your pipes are improperly vented, your drains will be sluggish.  Sluggish draining can be noisy as the water fights to move along.  It requires some air to permit a smoother water flow.

Can the washing machine drain into a sink?

The short answer to the question is yes.  Oftentimes, a laundry room will include a utility sink for handwashing of clothes, washing of hands, etc.  A washer can be drained into that sink. 

It’s possible to install the washing machine drain hose into the sink drain with the proper fittings and then secure the drain hose to the sink.  You will want to make sure the sink drain has the appropriate gauge to accommodate a clothes washers drain pump volume and pressure.

Assuming the plumbing is sufficient and that neither the main drain pipe nor the vent pipe is obstructed, there will be no gurgling.

Why does water come up the sink when the washing machine is on?

washing machine

But, what if water rises in the kitchen sink and it fills when the washing machine is draining?  That can’t be good, can it? 

No, it’s not good and is a sign that there is an obstruction preventing the water from flowing down the main drainage pipe: 

  • Either because the main drain pipe has a partial blockage; or,
  • The air vent is partially blocked; or,
  • Both.

So, if your sink fills up when the washing machine is draining, checking both of these possibilities is the course of action to follow.  A handy DIYer might be able to take care of this himself or herself.

A plumber, though, would likely recognize which of the causes is most likely just by listening to the gurgle, for instance.  Also, if it is an obstruction in the main drain line, a plumber would be your best bet for cleaning out the clog.  For water coming up into your kitchen sink, though, it is more likely to be that main drain line obstruction.

Venting About Your Gurgle From The Kitchen Sink

If your washing machine and your kitchen sink each have their own air or “dry” vents, they’ll connect to the main dry vent running up through the wall and out through the roof.  Perhaps, then,  the obstruction is in that main vent.  Again, the purpose of this vent is to allow air to enter the plumbing system for the smooth flow of water through the lines.  It is essential to every plumbing system.

If the air vent is blocked, negative pressure will develop and pull air from wherever it can.  Water from the draining washing machine will form an air-tight seal in the pipe as it flows.  A vacuum is formed, and the water pushes the air along ahead of it. 

This rushing air causes the gurgling sound you hear from the kitchen sink.

Get your ladder out and climb up on the roof to the vent pipe.  Perhaps some leaves or a small branch have fallen into it.  If you’re lucky, it’s close enough to the top of the pipe that you can clear it out by hand.

If it isn’t, bring your hose up and run some water down through the pipe.  Hopefully, the force of the water from your hose will be sufficient to dislodge the obstruction and carry it down the line and out through the main drain pipe to the sewer.

And, if that isn’t enough, you’ll need a long sewer auger to move it along.

Ridding Yourself of the Kitchen Sink Gurgle

We now know that some sort of obstruction causes the gurgle.  We know the blockage is in one of two places:

  • The main drain line, or
  • The vents
  • The studor vent – if you have one

An ambitious DIYer can sort out those two possibilities and perhaps find the cure. 

There are some products available from plumbing supply stores and the major DIY store venues that might help with the first possibility, the main drain line.  If you believe the obstruction is in the main drain line,  an enzyme-based, bacterial drain and trap cleaner might be the solution.

These products are easy to use and safe for your plumbing system.  They help break down accumulated grease, soap, and other organic materials that have clogged the pipe.

The store staff can help you make a good choice if you decide to go this route.  Follow the product instructions, and if you notice an improvement after application, you’ve found the cause and helped eliminate it.  After that, perhaps a regular application will keep your pipes happy and your kitchen drain quiet.

As for the vent stack obstruction, the solutions are a bit easier.  All you have to do is get up on your roof and either reach down or hose down.  One or the other will likely cure the ill and help keep your kitchen drain quiet, too.

The gurgle can be an annoyance, sure.  But the solutions aren’t too bad.  Follow these suggested steps and help yourself find peace and quiet in your kitchen.

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