Sunrise Specialty » How to Install a Tankless Water Heater? (Step-by-Step Tutorial)

How to Install a Tankless Water Heater? (Step-by-Step Tutorial)

Many homeowners love to use tankless water heaters for many reasons. First, it serves as an ideal way to produce heated water to their buildings. It also requires less space and helps reduce any utility bills.

However, installing a tankless water heater comes as a tricky job, except if you have basic technical skills. After all, you will need to have knowledge of various codes and the right parts to use. If you don’t feel up to this task, consider contacting a plumber.

Are you handy with tools? Well, this guide will show you how to install a tankless water heater.

How to Install a Gas Tankless Water Heater

Step 1: Take out Your Current Water Heater

Know the size of your gas main by contacting the gas company. Since this kind of heater uses more gas than large furnaces, you might have to connect a bigger pipe to the gas meter in your home.

Switch off the water and power supply to the current heater. You should also turn off the valves that supply gas to the unit. Drain and remove the heater from its mount before disposing or tossing it in a recycle bin.

Step 2: Fix New Water and Gas Lines for Your Heater

how to Install a Tankless Water Heater

If the existing gas line comes in a suitable size, fix a tee and a valve or one of them (as required). Use a black pipe to connect the new supply line near the gas line on your new gas tankless water heater. You can also use a flexible gas supply line for this task.

Use a copper pipe to connect old and existing water lines. Afterward, move the lines to the new tankless heater. You might place an expansion tank at the cold water inlet of the unit, mainly if the system has an anti-siphon or check valve.

Secure the pipes to the wall with some bell hangers. With these items, you can quickly use some pipe insulation.

Next, take out any oxidants by wiping the connectors and pipes. Then add some flux to the end of the piping, attach it to the connectors before fusing with a torch. Remember to heat the copper pipe before soldering.

Step 3: Place the Water Heater on a Stand

Purchase two pieces of lumber (with a measurement of 4 inches) and construct a platform. Experts recommend this size of lumber as it allows the unit to have a suitable spacing (of the same measurement) from the wall.

Look for a well-ventilated spot in the room and place the stand. Then, put your new water heater on the platform.

Step 4: Install the Water Heater

Install the Water Heater

Use the owner’s manual to attach the sediment trap and shutoff valve to the heater. Afterward, connect the gas supply line to the shutoff valve. Try to confirm if the water heater has the drain and purge valves.

Attach the valves on the heater to the water supply line and look for leaks by turning the water on. If none, repeat the checking procedure on the gas line. When completed, turn off the gas until you have finished setting up the unit.

5. Fix the New Vent

tankless water heater installation instructions

Look for the vent shaft of the unit and place some adhesive. For this stage, use silicone sealants that can handle the heat.

Next, add a connector and tighten with a hose clamp before slipping on a section of the vent pipe. Complete this assembly by placing a retaining ring on the tube. Fold over the taps for extra security.

Fix an elbow and ensure its mouth faces the same spot (on the outside) of the water heater vents. Bore a hole from inside the wall that will serve as an outlet for the unit.

Create the space by marking a circle on the outside wall with a vent thimble. Above the mark, use a spade bit to make a 1-inch hole.

Using a reciprocating saw, make the vent hole. From the hole, take out any sidings or shingles as this will help the flange thimble rest correctly on the outside wall. Add some silicone caulk on the end of the flange before pushing it into the opening. Tighten the assembly with screws (to the outer wall) and seal the fasteners with silicone.

From the inner wall, fix an interior flange before running a vent pipe through its mouth. Use tabs to keep all parts of the tube in position. Then, head to the outer wall and connect a part of the pipe with a vent hood. Round up by fixing the siding or shingles around the hole of the vent.

6. Switch on the Unit

Remove unwanted air from the plumbing and heater by running hot water from your faucet. After some minutes, switch off the water and connect the heater to a power supply.

Add some insulation to the pipe that carries hot water from the unit before switching on the gas. You can complete this stage by following the tankless water heater installation instructions in the owner’s manual. Now you know how to install a gas tankless water heater.

How to Install an Electric Tankless Water Heater


If you want a suitable alternative to a gas tankless water heater, consider choosing the electric model. Apart from working without vents, electric tankless water heaters are easier to install and require no gas combustion.

Since it works differently, you must know the electric tankless water heater installation requirements. To have this knowledge, consult the owner’s manual from time to time. Before using the following steps, purchase an electric model that suits your building.

Step 1: Disconnect the Power and Water Supply

Start by turning off the power on the unit. You should also detach the incoming water supply line from the heater. Ensure you place a container under the water bib to collect spills from the pipe.

Step 2: Remove the Water Heater from the Room

For an electric water heater, simply unplug the appliance from the wall outlet. Remove the plug of the existing heater from the power source. As soon as it’s free, dismount the unit and toss into the garbage or recycle bin.

Step 3: Connect the New Unit

Layout your new heater and look for the best spot to install it. When you find one, place the unit on a suitable platform and secure it with four screws. Even if you know other ways on how to install a tankless water heater, it’s advisable that you set it in an upright position.

Step 4: Connect the Unit to the Power and Water Supply

Rinse out the dirt from the pipe that supplies cold water. Then, attach the water heater outlet (on the left side of the heater) to the hot water line. Head to the right end of the heater, and then connect the cold water line to the cold water inlet.

Screw all the fittings on both sides of the heater and run all hot water faucets for 3 minutes. If you can’t find any leaks, use the following steps to connect the unit to a power source.

  • Connect a black and red wire to the breaker. But before fixing the wire pair, switch off the power to the heater with circuit breakers.
  • Use a wire gauge to run the power cable from the circuit breaker (in the central electrical panel) to the water heater. Connect the cable with the block terminal on the unit. After tightening every connection, screw in the front panel of your heater.

Step 5: Turn on the Water Heater

Clear out all the air in the power lines by running hot water faucets for 3 minutes. Then, switch on the power from the circuit breakers in the central unit. Now you can turn on the switch on the unit itself.

Tips for Installing an Electric Tankless Water Heater

Now that you have an idea on how to install a tankless water heater, consider the following tips for setting up a tankless water heater electric model.

  • If you use an electric tankless water heater, it needs an exhaust system with a large diameter. It will also work with a steel flue powered by high voltage. Remember to confirm this feature before installing the heater without using a professional.
  • For the plumbing, use union connector sets that you can bypass. Such items allow you to remove limescale from the heater with ease.

Wrap Up

Since tankless water heaters use less energy and have portable features, you should love this device. Besides, if you cannot call a professional to come set it up due to the tankless water heater installation cost, take the DIY steps.

To know how to install a gas tankless water heater, disconnect the old unit, and place it on a new platform. You should also check for leaks on the unit. You can also use this guide for tankless models that run on electricity.

Since the process requires technical skills, you should seek the services of a plumber or installer. If you find this article helpful, feel free to share it.

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