This Is Why Washing Machines Make Your Kitchen Sink Smell

This Is Why Washing Machines Make Your Kitchen Sink Smell

Are you haunted by smells in the kitchen sink on laundry day? No worries. Once you know why it happens and how to fix it, you can put those stinky days behind you.

Most sink smells are caused by sewage gases. When there’s a drain blockage or your home is not properly vented, the gasses find their way up the wrong pipe. You can fix the problem by removing blockages, cleaning or realigning vents, fixing drain traps or by cleaning the washing machine.  

Sure, you can call Bob The Plumber. But you can also fix this yourself. Here’s how to do it. 

The Source Of The Problem

If the kitchen sink smells bad when you do laundry, there are several reasons why this could be happening.  

What you’re smelling is most likely sewage gases being redirected into the house instead of safely going outside. Besides signalling that there is something wrong with the plumbing, it’s also bad news for one’s health. That rotten egg smell comes from hydrogen sulfide. Sewage gases can also include ammonia and carbon dioxide. Chronic exposure to these gases can lead to sewer gas poisoning symptoms like fatigue, headaches, nausea, and poor memory.

The sooner you find the source of the problem, the better! 

Luckily, the list of suspects is short. Most of the time, a blocked drain or vent is responsible. Cleaning the affected drain or vent will often remove the bad smell from your kitchen sink. Failing that, one can always investigate faulty drain traps or the possibility that the washing machine itself is Mr Smelly. 

How To Find And Fix A Faulty Vent Outside

In most cases, the exit point of a sewer vent pipe isn’t too hard to find. The pipe itself runs up to the roof and is located near the bathroom of the home. The vent takes gases upward and out into the air. But sometimes there is a blockage or a vent is not properly installed. This gives the bad smell an opportunity to creep back into the house. Since most washing machines are connected to the home’s venting system, using the washer could worsen the smell.

A faulty vent can either be blocked or improperly installed. You can climb on the roof and check the vent to see if last week’s storm stuck some leaves and twigs in there. Removing them will open the pipe and make your kitchen sink odour-free. Should you decide to clamber on the roof to check for debris in the vent pipe, please do so carefully. Falling off a roof can lead to serious injuries. Here are a couple of safety tips to keep in mind when you work on the roof.

How To Fix A Faulty Vent Inside

The vent system inside the home is usually slightly visible or completely hidden in the walls. Usually, when your washing machine causes the sink to stink, two things are responsible. 

  1. The venting pipes or drain system were incorrectly installed.
  2. The washing machine’s own pipe is interfering with the p-trap.

The Venting Pipes Or Drain System Was Incorrectly Installed

Hey, plumbers are human too. Sometimes, they make boo-boos. One of the most common mistakes they leave behind (sorry, plumbers), is a drainage system in the kitchen that does not properly connect with the venting system. There might even be a blockage somewhere. 

The fix is not as simple as fishing leaves and twigs from the vent’s outer grate (although that could help too). Some knowledge is required to either correctly hook the drain line to a working vent, install a new vent or clean a blockage from an internal pipe. 

But how does a washing machine trigger the bad smell in this case? If the kitchen drain or vent is not working properly, the running water from the washing machine sometimes builds enough pressure inside the drain to push gases past the pipe’s p-trap. Under normal circumstances, this curvy part of the pipe keeps sewer fumes from going the wrong way. But a blockage can also cause the p-trap to release gases which then escape through the kitchen sink (and sometimes the bathroom sink).

This Is Why Washing Machines Make Your Kitchen Sink Smell

A p-trap (plumbing-trap). Source.

The Washing Machine’s Own Pipe Is Interfering With The P-Trap

Another mistake that plumbers or homeowners make is when they install a new washing machine in the kitchen. Most washing machines have a plastic drain pipe that must be connected to the drainage system of the house. When the drainpipe is pushed too far in it can push past the p-trap. When that happens, the trap can no longer contain the sewer gases and they travel up to the kitchen sink. 

How do p-traps work? One must peek at their design to understand how to fix them. A p-trap is located at the curve under the sink. When water goes down the kitchen drain or the washing machine’s drain pipe, the p-trap fills with water. Once the trap is stuffed with H2O, it basically creates a seal that blocks sewer gases from taking the chance to sneak into the kitchen. 

There are several things you can try to get rid of the smell. Most p-traps are easily accessible but if yours aren’t, it might be a good move to call a professional plumber. 

  1. Reinstall the washing machine’s drain pipe so that it does not interfere with the p-trap’s effectiveness.
  2. Remove the p-trap to remove any potential blockages. If you have never done something like this before, here’s how to remove, clean, and re-attach your p-trap.

You can also look at the best under sink water filters if you want to improve the taste of your home’s water. 

The Washing Machine Might Cause A Kitchen Sink To Smell

Sometimes, a blocked drain or faulty vent is not behind the awful smell in your kitchen. Perhaps you checked the p-trap and found no blockage and the washing machine’s drain pipe is nowhere near it. So what could be the culprit? The washing machine. It might simply need a little maintenance to clear up the issue.

After months of use, a washing machine can develop several hiccups that might cause a bad smell.

  1. A blockage in the washing machine’s drainage pipe.
  2. A happy colony of mould or bacteria.
  3. A lack of routine maintenance.
  4. Hard water deposits.

How To Freshen Your Washing Machine And Get Rid Of Smells

If your washing machine is the source of the sewage smell, there is a silver lining. It is not real sewer gases trying to invade your home. Very often, the damp conditions of a washer can breed odours that are mistaken for sewage smells. That being said, one must still try and get rid of the smell. Not only is it unpleasant but it might also cause your laundry to reek. Hard water areas can also mess with drains and washing machines. 

This Is Why Washing Machines Make Your Kitchen Sink Smell

Baking soda effectively removes odours.

Option 1: Take half a cup of baking soda and half a cup of white vinegar. Add it to the loader but do not add clothing. Run the machine through a cycle and if you notice that the smell is better – but not completely gone – do the same thing but this time only with a cup of bleach. 

Option 2: Leave the doors and trays of your washing machine open when you’re not using it. This helps to fight a moist interior that mould and bacteria love so much.

Option 3: If your washing machine has a service spin option, you can use it to kill bacteria. The cycle uses high temperatures and if you do this roughly once a month, bacteria won’t stand a chance to breed to the point where you start to smell them.

Option 4: A sewage smell can also come from certain parts of the washing machine if they haven’t had maintenance in a while. It’s important to check things like door seals, heating elements, the filter, hose, drain, drum, and detergent tray for bacterial build-up.

Option 5: Sometimes detergent itself is a problem. When you use too much, globs can stay behind in the washing machine and create a perfect breeding ground for bacteria. This is especially true if you do not use enough water. Consider it a trial-and-error experiment to get the water-detergent ratio right but it’s well worth the effort. 

When It’s Time To Call The Plumber

A reputable company will have staff experienced in dealing with sticky situations. These include working on a dangerous roof, removing blockages from deep inside pipes, and dealing with p-traps that are glued and cannot be removed in a conventional manner. When you are faced with such troubles, calling a plumber might be a safe and faster way to get rid of the smell in your kitchen sink.

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About the Author Harry Thompson

Involved in home renovations throughout his life, Harry is an expert in everything to do with home and garden DIY. In his spare time, he enjoys cooking and tending to his garden.