How To Run New Plumbing In A House: A Step-by-Step Guide for Homeowners

Why You Need to Know How To Run New Plumbing In A House

Maybe you’re adding a bathroom to your basement. Or turning that unused closet into a laundry room. Perhaps you just bought an older home and the pipes are rusted, outdated, or just… nowhere near where you need them.

Whatever your reason, how to run new plumbing in a house isn’t just a DIY project—it’s a critical decision that affects your home’s safety, value, and daily comfort. And if you do it wrong? You could be looking at water damage, mold, code violations, or a $10,000 repair bill.

The good news? With the right plan, tools, and a little patience, you can do it yourself—safely and legally. This guide walks you through every step, backed by plumbing professionals, building codes, and real homeowner experiences.

1. Can You Really Run New Plumbing Yourself? (The Honest Answer)

Let’s cut through the noise: Yes, you can install new plumbing as a homeowner—but only under certain conditions.

According to the International Residential Code (IRC), most U.S. states allow homeowners to pull permits and do their own plumbing work on properties they occupy. But here’s the catch:

• You must obtain a permit (fines for unpermitted work can reach $5,000+).
• Inspections are mandatory at key stages (rough-in, final).
• Some cities (like NYC or San Francisco) require licensed plumbers for certain systems.

“Homeowners who skip permits often end up paying more in the long run—whether it’s when selling the house or during an insurance claim.”
— Mike Smith, Master Plumber & Inspector, 18 years experience

✅ Do-It-Yourself Friendly Projects:

• Adding a sink in a basement bar
• Installing a new toilet in a converted closet
• Running water lines to a backyard hose bib

🚫 Leave to Professionals:

• Main water line reroutes
• Gas line connections
• Sewer line extensions beyond your property line

Pro Tip: Call your local building department before you buy a single pipe. Ask:

• “What permits are required?”
• “Can I do this myself?”
• “What’s the inspection schedule?”

2. How Do You Plan the Layout for New Plumbing? (Avoid Costly Mistakes)

A bad layout = wasted money, awkward fixtures, and future headaches.

Step 1: Map Your Water & Drain Paths

Use graph paper or a free app like SketchUp Free to sketch your space. Ask yourself:

• Where will the fixture go? (sink, shower, washer)
• Where’s the nearest existing supply line or drain?
• Can you run pipes downward? (Gravity is your friend—drains must slope ¼” per foot.)

Step 2: Know the Minimum Clearance Rules

The IRC requires:

Source: International Residential Code – IRC Chapter 29

Step 3: Choose the Right Pipe Material

Not all pipes are created equal.

Recommendation for beginners: Start with PEX. It’s what 80% of new homes use today—and it’s the easiest to work with.

3. Step-by-Step: How To Run New Plumbing In A House (From Start to Finish)

Let’s say you’re adding a sink in your garage for a workbench. Here’s exactly how to do it.

Step 1: Shut Off the Main Water Supply

• Find your main shutoff valve (usually near water heater or where the line enters the house).
• Turn it clockwise until tight.
• Open a faucet downstairs to drain residual pressure.

Step 2: Cut Into the Existing Supply Line

• Use a pipe cutter or tubing cutter to make a clean cut in the nearest cold/hot water line.
• Install a T-fitting (PEX) or saddle valve (for copper) to branch off.

💡 Pro Tip: Always install shutoff valves at the fixture. That way, if your sink leaks, you don’t shut off the whole house.

Step 3: Run PEX to the New Fixture

• Measure the distance. Add 10% extra for bends.
• Use PEX crimp rings or push-fit connectors (like SharkBite) for tool-free installation.
• Keep pipes away from heat sources (furnace, water heater) by at least 6 inches.

Step 4: Install the Drain Line

• Run 1.5” or 2” PVC pipe from the sink tailpiece to the nearest drain stack.
• Slope it ¼ inch per foot toward the main line. Use a level and a string line to check.
• Connect with PVC cement and primer (follow manufacturer instructions).

Step 5: Vent the Drain (Critical!)

Every drain needs a vent to prevent suction and gurgling.
→ If you’re within 6 feet of an existing vent stack, you can tie into it with a wet vent.
→ Otherwise, install a air admittance valve (AAV)—a one-way valve approved by IRC 908.12.

“A missing vent is the #1 cause of slow drains in DIY jobs.”
— Plumbing Inspector, Chicago Building Department

Step 6: Test for Leaks

• Turn the water back on.
• Run water for 5 minutes.
• Check every joint with paper towels. If it’s damp, it’s leaking.
• Use a pressure gauge (available at hardware stores) to test for drops—under 2 PSI drop in 15 mins = good seal.

Step 7: Schedule Your Inspection

Call your city’s building department. Most offer same-day or next-day inspections.
Bring your permit number and a sketch of your work.

4. Common Mistakes to Avoid (Learn From Others’ Errors)

Here are the top 5 mistakes homeowners make when running new plumbing—and how to dodge them:

1. Skipping the Permit → Fines, failed home sale, insurance denial.
2. Ignoring Slope → Standing water → Mold → $5k remediation.
3. Using Too Many Fittings → Each joint is a potential leak point. Minimize bends.
4. Not Insulating Pipes → In cold climates, uninsulated pipes freeze and burst. Use foam sleeves.
5. Forgetting the Shut-Off Valve → Imagine turning off water to the whole house because of one leak.

Real Story: A homeowner in Ohio added a bathroom in his attic without a vent. Six months later, his toilet gurgled and backed up. Repair cost: $3,200. He could’ve paid $40 for an AAV.

5. When to Call a Professional (And What It Costs)

Even if you’re confident, some things are better left to pros.

Why hire a pro?

• They know local codes inside-out.
• They carry liability insurance.
• They can get materials faster (and cheaper) through trade discounts.

If you’re unsure, hire a plumber for a $75–$150 consultation. They’ll review your plan and tell you what you can do yourself.

FAQ: Your Top Questions About How To Run New Plumbing In A House

Q1: How long does it take to run new plumbing in a house?

A: For a simple sink addition, plan 1–2 days. Include drying time for glue (PVC takes 2 hours), inspection wait time, and testing. A full bathroom can take 3–7 days depending on walls and permits.

Q2: Do I need a permit to run new plumbing?

A: Yes, almost always. Unpermitted work can void your homeowner’s insurance and hurt your home’s resale value. Permits typically cost $50–$200, depending on your city.

Q3: Can I use PVC for water supply lines?

A: No. PVC is only for drains and waste. Use PEX, CPVC, or copper for supply lines. PVC cracks under pressure and isn’t rated for potable water in most codes.

Q4: How much does it cost to run new plumbing per foot?

A: Materials alone: $1.50–$4 per linear foot for PEX. Labor (if hired): $45–$150/hour. Total for a 20-foot run? Around $300–$700 if DIY, $800–$1,500 if hired.

Q5: What’s the easiest way to run plumbing through walls?

A: Drill holes through studs (max 40% of stud width, per IRC). Use a flexible PEX snake with a fish tape. Avoid drilling near electrical wires—use a stud finder with AC detection.

Q6: Can I run plumbing through the attic?

A: Yes—but insulate everything and avoid running lines where temperatures drop below freezing. Use heat tape in cold climates. Always vent through the roof, not the soffit.

Conclusion: You’ve Got This — And Your Home Will Thank You

Running new plumbing in a house isn’t magic. It’s planning, patience, and precision. Whether you’re adding a sink, a laundry station, or a full bathroom, following these steps will save you thousands and give you peace of mind.

You’re not just installing pipes—you’re improving your home’s functionality, safety, and value.

Ready to start?
👉 Take a photo of your planned layout.
👉 Call your city’s building department.
👉 Buy your PEX kit and a crimp tool ($30 at Home Depot).

And when you finish? Share this guide with a friend who’s thinking about a renovation. One helpful post can prevent a costly mistake.

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