Do You Need to Test Pressure When Upgrading Plumbing?

If you’re upgrading your home’s plumbing system—whether replacing old pipes, adding a new bathroom, or installing a tankless water heater—you might wonder: Do you need to test pressure when upgrading plumbing line? The short answer: absolutely yes. Skipping this critical step could lead to hidden leaks, property damage, or even code violations. In this guide, we’ll walk you through why pressure testing isn’t just recommended—it’s essential for a safe, reliable, and long-lasting plumbing system.

Why Is Pressure Testing Required After Upgrading Plumbing?

When you modify or install new plumbing lines, you introduce new joints, fittings, and connections—each a potential leak point. A pressure test verifies that your system can safely handle normal water pressure without leaking.

According to the International Residential Code (IRC) P2503.4, all newly installed water supply systems must undergo a hydrostatic pressure test before being put into service. This isn’t just bureaucracy—it’s a proven safety measure.

“A pressure test is the only reliable way to ensure your plumbing system won’t fail once walls are closed up,” says Michael Carter, a licensed master plumber with over 18 years of experience in California. “I’ve seen $10,000+ water damage claims from jobs that skipped this step.”

What Happens During a Plumbing Pressure Test?

A standard pressure test (also called a hydrostatic test) involves the following steps:

1. Isolate the system: Shut off the main water supply and disconnect any appliances (water heater, softener, etc.).
2. Seal all outlets: Cap off faucets, showerheads, and other endpoints.
3. Pressurize the system: Use an air compressor or water pump to bring the system to 50–80 psi—well above normal household pressure (typically 40–60 psi).
4. Hold and monitor: Maintain pressure for at least 15–30 minutes (local codes may require longer).
5. Check for drops: A stable pressure reading means your system is leak-free. A drop of more than 2–3 psi indicates a leak.

💡 Pro Tip: For copper or PEX lines, many inspectors require a minimum 15-minute test at 100 psi using air (not water) to avoid moisture-related issues during inspection.

What Types of Plumbing Upgrades Require Pressure Testing?

Not all plumbing work is equal—but most structural or supply-line modifications do. Here’s a quick reference:

Even minor upgrades involving new supply lines—like for a refrigerator ice maker or dishwasher—should be pressure-tested if they tie into the main system.

Risks of Skipping the Pressure Test

Think skipping a pressure test saves time or money? Think again. Consider these real-world consequences:

• Hidden leaks behind walls: Can cause mold, rot, and structural damage. The EPA estimates that 10% of homes have significant leaks wasting 90 gallons per day.
• Insurance denial: Many homeowners’ policies exclude water damage from untested or unpermitted plumbing work.
• Failed inspections: If you’re selling your home, an untested plumbing upgrade can delay closing or force costly re-dos.
• Wasted materials: A single pinhole leak can ruin drywall, flooring, and cabinetry—costing 5–10x more than the test itself.

How to Perform a DIY Pressure Test (Safely)

While licensed plumbers often handle this, handy homeowners can do a basic test—if local codes allow. Here’s how:

Tools You’ll Need:

• Air compressor or hand pump
• Pressure gauge (0–150 psi range)
• Threaded caps or plugs
• Teflon tape
• Safety goggles

Step-by-Step Instructions:

1. Turn off main water supply and drain existing water from pipes.
2. Remove aerators and disconnect appliances.
3. Seal all open ends with caps—use Teflon tape on threads.
4. Attach pressure gauge to an outdoor spigot or washing machine valve.
5. Pump air to 80 psi (or as required by local code).
6. Wait 15 minutes—do not exceed 24 hours for air tests (risk of pipe stress).
7. Observe gauge: No drop = pass. Any drop = inspect joints with soapy water (bubbles reveal leaks).

⚠️ Warning: Never use excessive pressure. PVC pipes can burst above 100 psi. When in doubt, consult a professional.

For more on plumbing system standards, see the International Plumbing Code overview on Wikipedia.

Common Misconceptions About Plumbing Pressure Tests

Let’s clear up a few myths:

• Myth: “If it doesn’t leak when I turn the water on, it’s fine.”
  Truth: Minor leaks may only appear under sustained pressure—especially in soldered or crimped joints.
• Myth: “Only commercial jobs need pressure tests.”
  Truth: Most U.S. municipalities require them for residential upgrades too.
• Myth: “Water testing is better than air testing.”
  Truth: Air is safer for pre-inspection tests—it won’t cause water damage if a fitting fails.

FAQ Section

Q1: How much does a professional pressure test cost?

A: Most plumbers charge $100–$250 for a standard residential pressure test, depending on system size and location. It’s often included in full repipe or renovation quotes.

Q2: Can I pressure test PEX, copper, and PVC the same way?

A: Not exactly. PEX and copper handle air or water tests well. PVC is more brittle—use lower pressure (50–60 psi) and avoid air tests if possible. Always follow manufacturer guidelines.

Q3: How long must pressure be held during the test?

A: Minimum 15 minutes per IRC, but some states (like Florida and California) require 2 hours for underground lines. Check your local building department.

Q4: What if the pressure drops slightly?

A: A 1–2 psi drop over 30 minutes may be due to temperature changes. But a consistent or rapid drop means a leak. Re-pressurize and inspect with soapy water or an infrared moisture detector.

Q5: Is a pressure test needed for drainage pipes too?

A: No—drain lines use a different test (a “smoke test” or water fill test). Pressure testing applies only to pressurized supply lines.

Q6: Can I skip the test if I’m doing the work myself?

A: Not legally in most areas. Even DIY plumbing usually requires inspection—and inspectors will not approve without proof of a successful pressure test.

Conclusion

So, do you need to test pressure when upgrading plumbing line? Unequivocally—yes. It’s a small step that prevents massive headaches, protects your investment, and ensures your home meets safety standards. Whether you’re a seasoned DIYer or hiring a pro, never treat this as optional.

✅ Peace of mind
✅ Code compliance
✅ Prevention of costly water damage

If this guide helped you understand the importance of pressure testing, share it with a friend who’s planning a home renovation! And don’t forget to pin it on Pinterest, tweet it, or send it to your contractor—because safe plumbing is something everyone deserves.

Got questions? Drop them in the comments below—we’re here to help!