How to Plumb a Hot Water Heater in an RV (Step-by-Step Guide)

There’s nothing worse than stepping into a freezing shower after a long day of hiking or boondocking—especially when you know your RV should have hot water. If you’re wondering how to plumb a hot water heater in an RV, you’re not alone. Many new and seasoned RV owners face this exact challenge, whether they’re replacing an old unit or installing one for the first time. The good news? With the right tools, clear instructions, and a little patience, you can get reliable hot water flowing through your rig in just a few hours.

Why Proper RV Water Heater Plumbing Matters

Before diving into the “how,” it’s essential to understand the “why.” Unlike residential water heaters, RV units operate under unique constraints: limited space, mobile vibration, variable water pressure, and dual fuel sources (propane and/or electricity). A poorly plumbed system can lead to:

• Leaks that damage cabinetry or flooring
• Inefficient heating (wasting propane or battery power)
• Airlocks that prevent proper water flow
• Safety hazards like backflow or overheating

According to the RV Industry Association, over 23% of RV service calls related to water systems stem from improper installation or plumbing errors—most of which are avoidable with correct setup.

What Type of RV Water Heater Do You Have?

Not all RV water heaters are the same. Knowing your model is critical before plumbing begins. The three main types are:

💡 Pro Tip: Most tutorials (including this one) focus on standard 6-gallon tank-style heaters, which account for over 80% of RV installations (per RVIA 2024 data).

For more background on how these systems work, see Water Heating on Wikipedia.

Tools & Materials You’ll Need

Gather these before starting:

• Adjustable wrench
• Teflon tape (plumber’s tape)
• Pipe thread sealant (for gas lines, if applicable)
• ½-inch PEX tubing or flexible stainless steel hoses
• Shut-off valves (inlet & outlet recommended)
• Pressure relief valve (if not pre-installed)
• Water pump bypass kit (optional but helpful)
• Bucket & towels (for spill control)

⚠️ Safety First: Always disconnect propane and shore power before working. Drain existing water lines to avoid flooding.

Step-by-Step: How to Plumb a Hot Water Heater in an RV

Follow these steps carefully—even small mistakes can cause big problems down the road.

Step 1: Remove the Old Unit (If Applicable)

• Turn off propane and electrical supply.
• Drain the existing tank using the low-point drain valve.
• Disconnect inlet (cold) and outlet (hot) water lines.
• Unscrew mounting brackets and remove the unit.

📌 Note: Take photos of the original plumbing layout before disassembly—it’s a great reference!

Step 2: Prepare the New Heater Location

• Ensure the mounting area is clean, dry, and structurally sound.
• Verify clearance: Most heaters need at least 4 inches of space around vents and access panels.
• Check that the flue (for propane models) aligns with the existing roof or sidewall vent.

Step 3: Install Inlet and Outlet Connections

• Wrap Teflon tape clockwise around male threads (3–4 wraps).
• Connect the cold water inlet (usually marked “C” or blue) to your RV’s fresh water line.
• Connect the hot water outlet (“H” or red) to the hot water distribution line.
• Use flexible hoses or PEX tubing—rigid copper can crack from road vibration.

✅ Best Practice: Install shut-off valves on both lines. This lets you service the heater without draining the whole system.

Step 4: Connect Gas Line (Propane Models Only)

• Use yellow gas-rated hose and pipe thread sealant (not Teflon tape!).
• Tighten fittings with a wrench—but don’t overtighten (brass fittings strip easily).
• Perform a soapy water leak test: Apply solution to joints; bubbles = leak.

Step 5: Wire Electrical Components (If Applicable)

• For electric or dual-fuel models, connect 120V wiring per manufacturer specs.
• Ensure the circuit is GFCI-protected (required by NFPA 1192 for RVs).
• Never skip grounding—the green wire must be secured.

Step 6: Fill & Test the System

1. Close the pressure relief valve.
2. Open a hot water faucet inside the RV.
3. Turn on the fresh water supply (or run the water pump).
4. Wait until water flows steadily from the open faucet—this purges air.
5. Once water runs clear, close the faucet.
6. Slowly open the pressure relief valve to confirm water fills the tank.
7. Restore power/propane and ignite per instructions.

🔥 Critical: Never turn on the heater empty—this can melt the tank in minutes.

Common Mistakes to Avoid

Even experienced DIYers slip up. Watch out for:

• Skipping the air purge: Causes “dry firing” and element burnout.
• Using standard plumbing tape on gas lines: Leads to dangerous leaks.
• Ignoring anode rods: In hard water areas, replace every 1–2 years to prevent tank corrosion.
• Overtightening fittings: Creates cracks or stripped threads.

Pros vs. Cons: DIY vs. Professional Installation

If you’re comfortable with basic plumbing and follow safety protocols, DIY is often worth it—especially for standard replacements.

FAQ Section

Q1: Can I install a residential water heater in my RV?

No. Residential units are too large, lack vibration resistance, and aren’t approved for mobile use. They also require different venting and electrical setups. Stick with RV-specific models certified by ANSI Z21.57 or similar.

Q2: How long does it take for an RV water heater to heat up?

A standard 6-gallon propane heater takes 10–20 minutes to reach 120°F (49°C). Electric-only models may take 30–45 minutes. Tankless units provide hot water in under 30 seconds but at lower flow rates.

Q3: Why is my RV water heater leaking from the bottom?

This usually means the tank is corroded or the drain plug isn’t sealed. If it’s an older unit (5+ years), replacement is safer than repair. Always check the anode rod first—it’s a cheap fix if still intact.

Q4: Do I need to winterize the water heater?

Yes! Even if you bypass the tank, residual water can freeze and crack the lining. Either:

• Drain it completely via the plug and pressure valve, OR
• Use non-toxic RV antifreeze pumped through the system.

Q5: Can I run my RV water heater on electric and propane at the same time?

Most modern dual-fuel models allow simultaneous operation for faster recovery. Check your manual—but generally, yes, it’s safe and efficient.

Q6: What’s the ideal water temperature setting?

120°F (49°C) is the sweet spot: hot enough for showers, but low enough to prevent scalding and reduce energy use. Higher temps accelerate tank corrosion.

Conclusion

Now that you know how to plumb a hot water heater in an RV, you’re ready to enjoy warm showers wherever the road takes you—whether you’re parked at a KOA or deep in the backcountry. Proper installation not only boosts comfort but also protects your investment and ensures safety on every journey.

🔧 Did this guide save you a service call? Share it with fellow RVers on Facebook, Pinterest, or Reddit! Your tip could help someone avoid a cold morning disaster. And if you’ve got questions we didn’t cover, drop them in the comments below—we love helping the RV community thrive.

Safe travels and hot showers ahead! 🚐💨