How to Plumb a Drain for a Washing Machine – DIY Guide

If your washing machine isn’t draining properly—or you’re installing a new unit in a basement, garage, or laundry room—you likely need to plumb a drain correctly. Many homeowners attempt this themselves but end up with backups, overflows, or even code violations. Fortunately, learning how to plumb a drain for a washing machine is manageable with the right tools, knowledge, and safety precautions. This guide walks you through every step, so you can avoid costly mistakes and keep your laundry running smoothly.

Why Proper Washing Machine Drain Plumbing Matters

Improper drain setup is one of the top causes of laundry room flooding. According to the Insurance Institute for Business & Home Safety, nearly 20% of home water damage claims stem from appliance-related leaks—many tied to faulty washer drains.

A correctly plumbed drain ensures:

• Efficient water removal during spin cycles
• Prevention of sewer gas backup (thanks to proper venting)
• Compliance with local plumbing codes (like the International Plumbing Code or IPC)

Skipping key steps—like installing a standpipe or air gap—can void your appliance warranty or even violate building regulations.

What You’ll Need: Tools & Materials

Before you begin, gather these essentials:

Tools:

• Adjustable wrench
• Pipe cutter or hacksaw
• Tape measure
• Level
• Drill (if mounting brackets)
• Plumber’s tape (Teflon tape)

Materials:

• 2″ PVC or ABS pipe (for standpipe)
• P-trap (1.5″ or 2″)
• Hose clamp (if needed)
• Washing machine drain hose (typically included with appliance)
• Wall straps or brackets
• Sanitary tee or wye fitting (for connecting to main drain line)

💡 Pro Tip: Always check your local building codes. In many U.S. jurisdictions, washing machine drains must connect to a 2-inch minimum diameter standpipe that’s 18–30 inches tall, with a P-trap below.

Step-by-Step: How to Plumb a Drain for a Washing Machine

Follow these steps carefully—precision prevents future headaches.

Step 1: Locate the Drain Connection Point

Identify where your home’s main drain line runs—usually near existing plumbing in the laundry area. If you’re adding a washer to a new location (like a basement), you may need to tap into a nearby soil stack or horizontal drain line.

⚠️ Never connect directly to a sewer line without a trap. This allows dangerous sewer gases to enter your home.

Step 2: Install the P-Trap

The P-trap is non-negotiable. It holds water to block sewer gases.

• Use a 1.5″ or 2″ P-trap (2″ is preferred for washing machines due to high flow rates).
• Connect it to a sanitary tee or wye fitting on the main drain line.
• Ensure the trap is no more than 24 inches below the standpipe outlet (per IPC guidelines).

Step 3: Build the Standpipe

The standpipe is the vertical pipe your washer hose drains into.

• Cut a 2-inch PVC or ABS pipe to 30 inches tall (minimum 18″, but 30″ reduces siphoning risk).
• Secure it vertically to the wall with brackets every 4 feet.
• Leave a 1–2 inch gap between the top of the standpipe and the washer hose—this acts as an air gap to prevent backflow.

📏 Exact Measurement: The top of the standpipe should be 30–36 inches above the floor to meet most U.S. code requirements and prevent siphoning during high-speed spins.

Step 4: Connect the Washing Machine Drain Hose

• Slide the rubber end of your washer’s drain hose into the standpipe.
• Do not seal it airtight—this would eliminate the necessary air gap.
• Use a hose clamp only if the manufacturer recommends it (most modern hoses don’t require one).
• Loop the hose into a “high loop” (secured above the washer’s water level) before it drops into the standpipe—this prevents siphoning during operation.

🔗 Authoritative Reference: The International Residential Code (IRC) P2709.2 specifies washing machine drain requirements, including standpipe height and diameter.

Step 5: Test for Leaks & Flow

Run a quick rinse cycle:

• Watch for leaks at all joints.
• Listen for gurgling (a sign of poor venting).
• Ensure water drains fully within 60 seconds—slow drainage indicates a clog or undersized pipe.

Common Mistakes to Avoid

When to Call a Professional Plumber

While this DIY project is doable for many, call a licensed plumber if:

• You need to cut into main drain lines
• Your home lacks proper venting
• Local codes require permits or inspections
• You’re installing in a slab foundation (may need jackhammering)

The average cost for professional washer drain installation ranges from $150–$400, according to HomeAdvisor (2023 data)—a small price to avoid $5,000+ in water damage.

FAQ Section

Q: Can I drain my washing machine into a sink or bathtub?

A: Temporarily, yes—but it’s not recommended long-term. High-volume discharges can overwhelm sink drains, cause backups, and violate plumbing codes. Always use a dedicated 2″ standpipe with a P-trap.

Q: How high should the washing machine drain hose go?

A: Create a “high loop” by securing the hose at least 30 inches above the floor (higher than the washer’s tub). This prevents siphoning. The hose then drops into the standpipe.

Q: Do I need a vent for my washer drain?

A: Yes. All fixtures require venting to equalize pressure. If your drain line isn’t near an existing vent stack, you may need an Air Admittance Valve (AAV)—check local code approval first.

Q: Why does my washer smell like sewage?

A: Likely causes: a dry P-trap (pour 2 cups of water down the standpipe monthly) or missing trap. Sewer gases enter when the trap seal evaporates or is absent.

Q: Can I share a drain with a kitchen sink?

A: Not advisable. Washing machines discharge 15–25 gallons per cycle rapidly—far more than sinks. Shared drains often lead to backups. Use a dedicated line.

Q: What’s the maximum length for a washer drain hose?

A: Most manufacturers limit it to 6–10 feet. Longer runs reduce drainage efficiency and increase clog risk. Keep it short and sloped downward.

Conclusion

Now you know exactly how to plumb a drain for a washing machine—safely, efficiently, and up to code. A properly installed system protects your home from water damage, keeps sewer gases out, and ensures your appliance runs at peak performance.

✅ Key takeaways:

• Always use a 2″ standpipe (30–36″ tall)
• Never skip the P-trap
• Maintain an air gap—don’t seal the hose
• Follow local plumbing codes

If this guide saved you a plumbing disaster, share it with a friend who’s tackling laundry room upgrades! And don’t forget to pin it for your next DIY project. Happy plumbing! 🛠️💧