How To Plumb In A Dishwasher And Washing Machine Together (Step-by-Step Guide)

Why You Might Want to Plumb Your Dishwasher and Washing Machine Together

If you’re living in a small apartment, remodeling a kitchen, or just trying to maximize limited space, you’re not alone. Over 68% of U.S. households in urban areas have limited plumbing access, according to the U.S. Census Bureau’s 2023 Housing Survey. Many homeowners and renters are asking: Can I plumb my dishwasher and washing machine together?

The short answer? Yes — but only if done correctly.

Plumbing both appliances to a single water supply and drain line isn’t just a space-saver — it can cut installation costs by up to 40% and reduce clutter under your sink. But get it wrong, and you risk leaks, mold, or even flooding your kitchen.

In this guide, we’ll walk you through how to plumb in a dishwasher and washing machine together — safely, legally, and with confidence. Whether you’re a DIY newbie or a seasoned handyman, you’ll walk away with a clear, step-by-step plan backed by plumbing professionals and real-world results.

Can You Really Share One Water Line and Drain for Both Appliances?

This is the #1 question people ask — and the answer isn’t a simple yes or no.

Yes, you can share a water supply line — but only with proper fittings and pressure management.
No, you cannot share a drain line without a proper air gap and trap setup — or you’ll violate plumbing codes and risk sewage backup.

The International Residential Code (IRC) Section P2705.1 requires all drain connections to have an air gap to prevent backflow contamination. That’s why many DIYers fail — they connect both appliances directly to the same drain pipe without a standpipe or Y-fitting with an air gap.

“Sharing a water supply is common in European homes, but in the U.S., the key is pressure regulation and drainage separation,” says Mike Henderson, a licensed plumber with 18 years in California. “A single 3/4-inch supply line can handle both, but the drain must be vented and elevated.”

Here’s what you’ll need to make this work:

💡 Pro Tip: Always use brass or stainless steel fittings — plastic can crack under pressure or heat, especially near the dishwasher’s hot water inlet (up to 160°F).

Step-by-Step: How To Plumb In A Dishwasher And Washing Machine Together

Follow these 7 precise steps. Take your time — rushing leads to leaks.

Step 1: Turn Off Water and Power

• Shut off the main water supply under your sink.
• Unplug both appliances.
  Never work on plumbing while appliances are powered.

Step 2: Remove Existing Drain and Supply Lines

• Disconnect the dishwasher’s drain hose from the garbage disposal or sink drain.
• Remove the washing machine’s inlet hoses and drain hose.
• Cap the existing drain pipe temporarily to prevent debris from falling in.

Step 3: Install a T-Fitting for Water Supply

• Cut your cold water supply line under the sink (use a pipe cutter).
• Install a brass T-fitting with two integrated shut-off valves.
• Connect one outlet to the washing machine’s cold inlet (usually labeled “C”).
• Connect the other to the dishwasher’s inlet (usually marked “Hot” — yes, dishwashers often use hot water for better cleaning).

💡 Why Hot Water for Dishwasher?
The EPA recommends dishwasher inlet temperatures between 120°F–160°F for optimal sanitization. Most dishwashers heat water internally, but starting with hot water saves energy. Washing machines usually use cold — so this split is ideal.

Step 4: Set Up the Drain System — The Critical Part

This is where most DIYers mess up.

• Install a Y-fitting drain connector (3/4″ inlet, 2″ outlet) into your sink’s drainpipe.
• Attach a standpipe (a vertical PVC pipe) to the Y-fitting — minimum 30 inches tall.
• Connect the dishwasher’s drain hose to one side of the Y-fitting.
• Connect the washing machine’s drain hose to the other side.
• Crucial: Leave a 2-inch air gap between the top of the standpipe and the bottom of the hose loop. This prevents siphoning.

✅ Code Check: This setup meets IRC P2705.1 and UPC 804.4 for backflow prevention. Learn more about plumbing codes on Wikipedia .

Step 5: Secure Hoses and Prevent Kinks

• Use hose clamps on all connections — tighten until snug, but don’t over-torque.
• Route hoses so they don’t bend sharply. Kinks = restricted flow = pump failure.
• Keep dishwasher drain hose elevated in a “high loop” (at least 20 inches above floor) to prevent backflow.

Step 6: Test for Leaks — Don’t Skip This!

• Turn water back on slowly.
• Run a short cycle on the washing machine (no clothes, just water).
• Then run a rinse cycle on the dishwasher.
• Check every connection for drips. Use paper towels to detect moisture.

🔍 Real-World Tip: One homeowner in Austin, TX, saved $1,200 on professional installation by following this method — but had to redo it after skipping the air gap. “The drain backed up into my sink during the wash cycle. Lesson learned,” she told Home Repair Today.

Step 7: Inspect and Document

• Take a photo of your setup for future reference or home inspections.
• Label your shut-off valves: “Dishwasher – Cold,” “Washing Machine – Cold.”
• Keep receipts for fittings — some municipalities require proof of code-compliant materials.

Pros and Cons: Is This Setup Right for You?

Best For:

• Renters with landlord approval
• Small kitchens or laundry nooks
• Homeowners on a tight budget

Avoid If:

• Your home has old, low-pressure plumbing (<40 PSI)
• You’re in a multi-story building with shared drains
• You’re not comfortable with basic plumbing tools

FAQ: Your Top Questions Answered

Q1: Can I connect a dishwasher and washing machine to the same water supply?

Yes — as long as you use a T-fitting with individual shut-off valves and a 3/4-inch main line. Most modern homes have sufficient pressure (45–80 PSI) to run both simultaneously. If your water pressure drops below 30 PSI when both are running, you may need a pressure booster.

Q2: Do I need a special drain setup?

Absolutely. You must use a Y-fitting with an air gap connected to a standpipe at least 30 inches tall. Never connect both hoses directly to the same drain pipe without separation — it’s illegal in most U.S. jurisdictions and a health hazard.

Q3: Will this setup cause water pressure issues?

Not if done right. A 3/4-inch supply line delivers ~12–15 GPM — more than enough for a dishwasher (2–3 GPM) and washing machine (1.5–4 GPM). But if you have an older home with galvanized pipes, consider upgrading to PEX.

Q4: Can I use the same drain for both appliances at the same time?

No. Never run both appliances’ drain cycles simultaneously. The drain line can’t handle the combined flow (up to 8–10 GPM). Always stagger cycles — run the washer first, then the dishwasher 30 minutes later.

Q5: Do I need a permit for this?

It depends. In most U.S. cities (like Chicago, NYC, or Seattle), any permanent plumbing modification requires a permit. Check with your local building department. DIY without a permit can void home insurance.

Q6: What if I live in an apartment?

Many landlords prohibit DIY plumbing. Always get written approval. If allowed, use a non-permanent, hose-and-clamp setup with quick-release fittings. Avoid cutting pipes — use a sink-mounted diverter valve instead (available at Home Depot for under $25).

Final Thoughts: Save Space, Save Money — Do It Right

Plumbing your dishwasher and washing machine together isn’t just clever — it’s smart. In a time when space is premium and sustainability matters, this setup reduces material waste, cuts installation costs, and keeps your kitchen tidy.

But remember: speed doesn’t equal safety. Take your time. Follow the codes. Use the right fittings. And when in doubt — hire a licensed plumber for a $75 inspection. A small investment now prevents a flooded kitchen later.

If this guide helped you save time, money, or stress — share it with a friend who’s struggling with their kitchen layout. Tag them on Instagram or Pinterest with #PlumbSmart and help others avoid costly mistakes.

Did you try this setup?
Drop a comment below with your experience — or upload a photo of your installation! Your story could help someone else succeed.