Can I Add a Bathroom Tap to Laundry Room Plumbing?

You’re not alone if you’ve ever stared at your laundry room and thought, “Could I add a bathroom tap here?” Maybe you’re tired of trekking to the main bathroom during laundry day—or perhaps you’re converting part of your utility space into a half-bath or mudroom. The good news? Yes, you can add a bathroom tap into laundry room plumbing—but it’s not always as simple as connecting a faucet. In this guide, we’ll walk you through everything you need to know to do it safely, legally, and efficiently.

Is It Possible to Tap Into Laundry Room Plumbing for a Bathroom Sink?

Short answer: Yes—with caveats.

Laundry rooms typically have both hot and cold water lines feeding the washing machine, along with a drain and vent system. These existing utilities can often support a bathroom sink—but only if they meet plumbing code requirements for fixture units, pipe sizing, and venting.

According to the Uniform Plumbing Code (UPC) and International Plumbing Code (IPC)—the two primary standards adopted across U.S. states—a sink requires:

• A dedicated cold and hot water supply (½-inch diameter is standard)
• A properly vented 1½-inch drain line
• An approved P-trap to prevent sewer gases

If your laundry setup already includes these (or close equivalents), you’re in a strong position to add a tap.

💡 Pro Tip: Always check with your local building department first. Codes vary by city—even within the same state.

What Are the Key Plumbing Requirements?

Before you grab your wrench, understand what’s actually required:

1. Water Supply Lines

Most washing machines use ¾-inch hoses, but sinks need only ½-inch supply lines. You can tee off the existing hot and cold lines using a ½-inch brass tee fitting. Ensure you install shut-off valves for the new faucet—this is required by code and makes future repairs safer.

2. Drain and Vent System

This is where most DIYers run into trouble. A laundry standpipe (the tall pipe behind your washer) is designed for high-volume, intermittent flow—not the steady, low-volume drainage of a sink.

• Drain: You’ll typically need to run a new 1½-inch drain line from the sink to the main stack or tie into the washer drain above the P-trap (never below!).
• Vent: Every fixture needs a vent to equalize air pressure. If your laundry room isn’t near a vent stack, you may need an Air Admittance Valve (AAV)—allowed in many (but not all) jurisdictions. [Learn more about plumbing vents on Wikipedia](https.

3. Fixture Unit (FU) Load

Plumbing codes assign “fixture units” to quantify drainage demand. A washing machine = 2 FUs; a lavatory sink = 1 FU. Your existing drain line must handle the combined load. A standard 2-inch laundry drain can support up to 6 FUs—so adding a sink is usually fine, but verify with a pro if you’re near capacity.

Step-by-Step: How to Add a Bathroom Tap to Your Laundry Room

Follow these steps for a code-compliant, leak-free installation:

Step 1: Turn Off Water & Drain Lines

Shut off the main water supply. Open the washer valves to relieve pressure and drain residual water.

Step 2: Install Supply Line Tees

• Cut into the existing hot and cold lines near the washer hookup.
• Solder (copper) or press-fit (PEX) a ½-inch tee upstream of the washer valves.
• Add ½-inch quarter-turn shut-off valves for the new sink.

Step 3: Run New Drain Line

• Position the sink so its P-trap is 6–18 inches above the floor (standard height).
• Connect a 1½-inch PVC drain from the sink tailpiece to a new sanitary tee on the main drain stack—or tie into the washer drain above its P-trap.
• Never share a P-trap between sink and washer—that violates code and causes odors.

Step 4: Vent the Fixture

• If within 5 feet of a vent stack, tie directly into it.
• If not, install an AAV (e.g., Studor Mini-Vent) under the sink—mounted at least 4 inches above the P-trap flood level.

Step 5: Test for Leaks & Drain Flow

• Turn water back on slowly.
• Run water for 5+ minutes, checking all joints.
• Fill the sink and drain it quickly—watch for gurgling (a sign of poor venting).

⚠️ Warning: Skipping permits or inspections can void home insurance or complicate future sales. In 2023, 32% of failed home inspections cited unpermitted plumbing work (National Association of Home Builders).

Pros and Cons: Adding a Tap vs. Installing a Full Half-Bath

If you only need hand-washing access (e.g., for gardening, pet care, or crafts), a single tap makes sense. But if you’re planning long-term upgrades, consider roughing in space for a toilet too.

Common Mistakes to Avoid

1. Tapping into the washer’s drain below the P-trap → causes sewer gas leaks.
2. Using washing machine hoses for the sink → they’re not rated for constant pressure.
3. Ignoring local codes on AAVs → some cities (e.g., Los Angeles) ban them indoors.
4. Skipping a permit → can lead to fines or forced removal.

FAQ Section

Q1: Do I need a permit to add a sink in my laundry room?

A: In most U.S. municipalities, yes. Any new plumbing fixture typically requires a permit and inspection to ensure compliance with health and safety codes. Check your city’s building department website—many offer online applications.

Q2: Can I use the same drain as my washing machine?

A: Only if you tie into the drain line above the washing machine’s P-trap. Connecting below traps sewer gases and violates plumbing code. A shared drain without separate traps is a common code violation.

Q3: How much does it cost to add a bathroom tap to a laundry room?

A: DIY costs range from $200–$600 (faucet, piping, fittings). Hiring a plumber typically costs $450–$1,200, depending on complexity and location (HomeAdvisor, 2024).

Q4: Will this affect my water pressure?

A: Minimally—if done correctly. Use ½-inch supply lines and avoid excessive bends. If you notice pressure drops when both washer and sink run, your main line may be undersized (common in homes built before 1980).

Q5: Can I install a sink without a vent?

A: No. Every plumbing fixture must be vented to prevent siphoning of trap water and sewer gas entry. If traditional venting isn’t possible, an AAV is a legal alternative in most areas—but confirm with local code.

Q6: What type of faucet works best?

A: A widespread or centerset bathroom faucet (not a utility sink model) gives a clean look. Choose one with ¼-turn ceramic disc valves for durability. Avoid pull-down kitchen faucets—they’re overkill and harder to install in tight spaces.

Final Thoughts

So, can you add a bathroom tap into laundry room plumbing? Absolutely—provided you respect plumbing codes, venting rules, and local regulations. It’s a practical, budget-friendly upgrade that adds convenience without a full remodel.

Done right, this small addition can make laundry day easier, support a future mudroom conversion, or even boost your home’s functionality for aging-in-place.

Found this guide helpful? Share it with a friend or on social media—someone out there is Googling the same question right now! 💧🔧

Remember: When in doubt, consult a licensed plumber. Your safety—and your home’s value—is worth the extra assurance.