Can A Washing Machine And Bathtub Share The Same Drain?

Plumbing your home can be challenging, and figuring out drain configurations can be just as tricky, so it’s essential to do it correctly. This includes knowing what appliances can share drains, and which ones shouldn’t. So, can a washing machine and bathtub share a drain effectively?

A washing machine and bathtub can technically share the same drain. However, this isn’t recommended and will cause many plumbing problems later. Additionally, sharing the drain with the bathtub can be a housing code violation in some areas. A washer needs its own drain to ensure functionality.

Can A Washing Machine And Bathtub Share The Same Drain

In the rest of this article, I’ll discuss in greater detail why you shouldn’t force your bathtub and washing machine to share a drain, go over some drain requirements, and answer a few frequently asked questions about plumbing your washer. Let’s get started.

Why a Washing Machine and Bathtub Shouldn’t Share a Drain

There are several reasons you shouldn’t make a washing machine and bathtub share the same drain.

First, plumbers don’t recommend it as it may leave you with more work in the long run when something blocks the pipes.

Some of the other reasons sharing a drain is a bad idea include the following:

  • It’s against some home codes. This type of drain won’t pass home inspections in some areas, so it’s essential to double-check with your area before starting this DIY project. You don’t want to have to redo it all later if you decide to sell the property.
  • Bathtubs and washing machines require different-sized drain pipes. Generally, a bathtub drain needs to be 1 ½ inches in diameter (3.81 cm). In contrast, washing machine pipe requirements vary based on the brand and age of the model. More modern washing machines require larger drain pipes.
  • The drain will clog more easily. Because bathtubs and washing machines see so much debris, the likelihood of a clog is doubled. Both items will be hard on the drain, and if a clog occurs, both items will likely be unusable until fixed.
  • Running your tub and washer at the same time would be difficult. It’s not recommended to run the two simultaneously if you hook a washer and tub to the same drain because flooding is a risk.
  • Water might back up into either if a clog occurs. If a clog happens, water will likely back up into the washing machine or the bathtub rendering it useless until fixed. In this case, it’ll need flushing or the pipes redone.

As you can see, there are many reasons to avoid using the same drain for both household items.

So it’s better to do the job correctly the first time, especially if you don’t want to deal with repair costs down the road.

Washing Machine Drain Requirements

Can A Washing Machine And Bathtub Share The Same Drain

To successfully install your washing machine, it needs a proper drain.

If your home’s already plumbed for a washer, you won’t have to worry about the piping and drains.

However, if you add in a drain, you must meet a few requirements.

Necessary washing machine drainage parts include:

  • Traps. A trap is a curved portion of pipe that creates a water seal, preventing horrible smells from reaching you from the sewer.
  • Drain line. This line connects the other lines directly into the home’s main drain line.
  • Vent. A vent’s job is to prevent air from blocking the water’s flow. Blocked water flow can cause backups and even gross sewer gasses to back up into the home.
  • Standpipe. A standpipe is used to drain the water directly into the sewer pipes.
  • Outlet box. A small metal box connects most of the plumbing. This box also serves as a quick shutoff in an emergency.

Without all these essential parts, your washing machine will have difficulty draining correctly, and there’s a higher chance of sewer smells making their way back into your home.

Does a Washing Machine Need a Dedicated Drain?

Can A Washing Machine And Bathtub Share The Same Drain

So since installing washers to share a drain with bathtubs is frowned upon, what’s the best course of action? Can you utilize another drain, or does your machine need its own?

A washing machine does need a dedicated drain to function at total capacity, especially if it’s a newer model. Typically, your washer will need to have a vented standpipe installed to ensure proper drainage and prevent unwanted blockages. The piping size will vary based on age and washer model.

When in doubt, it’s best to bring in a professional.

Plumbers regularly deal with these kinds of installations and can install a drain specifically for your washing machine unit to use.

Can a Washing Machine and Sink Share a Drain?

You may have encountered instructions about washing machines and sinks sharing a drain during your plumbing research, but is it a good idea? Can a washing machine and sink share a drain successfully?

A washing machine and sink can technically share a drain, and many do, but this isn’t recommended. Sharing a drain often leads to clogging, and you must juggle which item is in use. However, while it’s common for utility sinks and washers to share a drain, it’s best that a washer have its own drain.

Again, you’ll have to do what you deem as best.

Sharing a drain with a sink is less problematic than sharing a bathtub.

Utility sinks commonly share a drain with washers since they’re often included in modern laundry rooms.

Consulting a professional is always a good idea and will help determine if you can safely connect the two drains.

Where Should a Washing Machine Drain To?

A washing machine should drain into a home’s main sewer line, which drains into the city’s larger sewer system. However, in more rural areas, your waste will likely drain into a separate system known as a dry well. Because of the harsh cleaners used in washers, the water needs proper disposal.


While you can make a washing machine and bathtub share the same drain, it’s not recommended since it often results in several problems like blockages and sewer smells reaching your home through the pipes.

It’s best to give washing machines their own drain pipes since they require larger ones, especially the newer models.

Also, with its own drain, you’re far less likely to have to make plumbing repairs down the road.

Cheers, tools owners!

Hi there! My name is Jack and I write for ToolsOwner. I have a passion for everything related to tools and DIY projects around the house. You often find me in my workshop working on new projects.