How to Install a Propane Tankless Water Heater

How to Install a Propane Tankless Water Heater

Switching to a propane tankless water heater is one of the smartest upgrades a homeowner can make. On-demand heating means you get hot water exactly when you need it โ€” no tank to maintain, no standby energy loss, and no cold showers when demand spikes.

Tankless Water Heater Installation Guide | A.O. Smith

Understanding Propane Tankless Water Heaters

Unlike conventional storage-style tanks that keep a large reserve of water hot around the clock, propane tankless units heat water only as it flows through the system. The result is instant, continuous hot water delivered precisely on demand โ€” a fundamentally more efficient approach to home water heating.

These compact, wall-mounted units are built for durability and performance. With proper care, a quality propane tankless heater will outlast a traditional tank water heater by many years, making it both an economical and environmentally responsible long-term investment.

Benefits of Going Tankless

Energy Efficient

Water is only heated when a tap is opened, eliminating the energy drain of keeping a tank hot 24/7.

Endless Hot Water

Hot water flows continuously for as long as you need it โ€” perfect for large families or high-demand use.

Space Saving

Wall-mounted and compact, these units free up significant floor space compared to bulky storage tanks.

Long Lifespan

Tankless heaters typically outlast conventional units by 5โ€“10 years, offering superior long-term value.

Lower Bills

Reduced energy consumption translates directly to meaningful savings on monthly utility bills.

How to Install a Tankless Gas Water Heater - The Home Depot

How Propane Tankless Heaters Work

The operating principle is elegantly simple โ€” water flows in, heat is applied on demand, and hot water exits to your fixtures. Here's the sequence:

Tap Opens

Opening a hot water tap signals the unit to begin the heating process.

Flow Detected

An internal flow sensor detects incoming water movement and activates the heating element.

Burner Ignites

The propane gas burner fires up and rapidly heats water as it passes through the heat exchanger.

Hot Water Delivered

Heated water exits the unit and flows to your fixture at the set temperature.

Tap Closes

The unit shuts down immediately, conserving both gas and energy until the next demand cycle.


Preparing for Installation

Careful preparation is the foundation of a safe and successful installation. Before you pick up a wrench, make sure you've addressed each of the following areas.

Choosing the Right Unit

Selecting the correct heater for your home is the most important decision in this process. Consider these factors:

Calculate your peak hot water demand to determine the required flow rate in gallons per minute. Factor in your local groundwater temperature โ€” colder climates require a unit with higher BTU output to achieve the desired rise. Confirm the unit's physical dimensions work for your intended installation location, and always verify compliance with local building codes before purchasing.

How to Install a Tankless Gas Water Heater - The Home Depot

Tools & Materials You'll Need


Copper pipe & fittings

Mounting hardware

Pipe joint compound

Pipe wrench

Propane torch

Threaded iron pipe & fittings

Teflon tape

Tubing cutter

Union fitting

Ventilation materials (if required)

โš  Safety Precautions โ€” Read Before Starting

  • Ensure adequate ventilation in the work area at all times
  • Keep a fire extinguisher within reach throughout the installation
  • Shut off the propane supply at the meter or tank before beginning
  • Turn off the main water supply and fully drain the existing water heater
  • Wear appropriate PPE โ€” gloves, safety glasses, and closed-toe footwear

Step-by-Step Installation

Follow these steps carefully and in order. If you're unfamiliar with gas line work, consult a licensed plumber or gas technician for the propane connections.

01
Shut Off the Main Water Valve

Close the main water supply at the meter to prevent water flow during the installation.

02
Disconnect & Remove the Old Heater

Cut the existing water supply lines connected to the old unit and carefully remove it from the wall.

03
Mount the New Unit

Secure the tankless heater to the wall using the provided mounting hardware, ensuring it is plumb and level.

04
Connect the Gas Line

Run threaded iron pipe from the outdoor propane tank to the heater. Tighten all fittings securely with a pipe wrench, and use Teflon tape or pipe joint compound on all threaded connections.

05
Attach a Union Fitting

Install a union fitting on the gas pipe โ€” this allows for easy disconnection during future maintenance without cutting lines.

06
Run Copper Water Lines

Connect copper supply lines from the home's existing water supply to the unit. Solder all copper connections cleanly and allow them to cool fully before proceeding.

07
Restore Water & Check for Leaks

Open the main water valve, restore the propane supply, and inspect every connection point carefully for signs of leaks before proceeding.

08
Power On & Configure

Plug in the unit, turn on the propane, and power on the heater. Set your desired water temperature to 120ยฐF at the heater's control panel for safe and efficient operation.


Routine Maintenance & Troubleshooting

Regular maintenance keeps your propane tankless water heater performing at peak efficiency and extends its operational lifespan significantly.

Annual Tasks
  • Flush the system to remove mineral buildup
  • Inspect and clean the burner assembly
  • Tighten all pipe and gas connections
As Needed
  • Clean or replace the inlet water filter
  • Inspect venting for obstructions
  • Check ignition system for wear
Monitor Regularly
  • Review error code log if displayed
  • Watch for unusual noises at ignition
  • Verify temperature consistency

Common Problems & Solutions

Fluctuating water temperature
Clean the inlet filter and verify gas pressure is within spec. Inconsistent pressure from the propane supply is the most common culprit.
No hot water output
Confirm the propane supply is open, check that the gas line connection is secure, and verify that water flow is reaching the unit.
Strange rumbling or rattling noise
This typically indicates mineral scale buildup in the heat exchanger. Flush the system with a descaling solution to resolve the issue.
Error codes on the display panel
Refer to your unit's owner manual for a full list of error codes and their corresponding corrective actions specific to your model.
Ready to Upgrade?

Make the Switch to On-Demand Hot Water

The Eccotemp Builder Grade Outdoor Liquid Propane Tankless Water Heater delivers reliable, efficient performance for residential and light commercial use.

Eccotemp 7GB-LP Tankless Heater
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