How to Install an Instant Hot Water Heater

Instant hot water heaters provide hot water on demand. Unlike traditional tank water heaters, which store hot water at the ready for use, instant heaters heat the water and immediately deliver it to an opened hot water faucet. These tankless water heaters can reduce electric consumption by heating water only when needed rather than maintaining a volume of water at temperature. Mount your hot water heater on an exterior wall so the you can properly vent it with the least amount of ductwork.

Difficulty: Challenging

Instructions

Things You'll Need:

• Drill
• 3/8-inch-diameter masonry bit
• Large-diameter masonry hole saw
• Mechanic's wrench or socket set
• Small bubble level
• Copper tubing and joints
• Bucket
• Black iron pipe for gas installation, or sheathed electric cabling for electric installation
• Solder
• Soldering torch
• One helper

1. Determine the installation site for the new instant water heater. Adhere to local codes pertaining to clearances, as well as minimum and maximum distances from utilities, walls and other structural components.

2. Mark the position of the vent hole on the exterior wall using the template provided with the water heater unit. Also mark the location of the water heater unit. Using a 3/8-inch-diameter masonry bit, drill a pilot hole through the wall at a position that is centered on the vent hole.

3. Drill the hole for the vent using a drill and a large-diameter masonry hole saw of a size recommended by the water heater's manufacturer. Drill about halfway through the wall from the inside, then go outside to drill the rest of the hole through the wall.

4. Run the gas or electric service to the water heater location using black iron pipe for gas installation, or sheathed electric cabling and conduit for electric installation.

5. Mount the water heater to the wall at the location marked from step 2 using the template. Use the brackets and bolts provided with the unit. Use the bubble level to be certain the unit is level.

6. Assemble the vent pipe. Mount the elbow of the vent pipe at the top of the heater. Have your helper go to the exterior side of the wall and attach the exterior part of the vent pipe. Have the helper then slide the exterior section of vent pipe into the vent hole and attach it to the heater's elbow.

7. Connect the gas lines or electrical connections to the water heater unit.

8. Turn off the water supply. Connect the water supply line from the home's plumbing system to the new water heater unit using copper tubing and any necessary copper piping joints. Use a torch and solder to sweat the joints and connect the piping.

9. Connect the outgoing hot water line from the new water heater to the home's plumbing system using copper tubing and any necessary copper piping joints. Use a torch and solder to sweat the joints and connect the piping.

10. Turn on the water supply. Test for leaks.

11. Place a bucket under the valves on the bottom side of the water heater unit, then open the valves to purge air from the plumbing lines. Close the valves after you've purged the air.

12. Turn on a hot water faucet in the house and verify that the new hot water heater functions as expected.

Tips & Warnings

• The mounting procedures are not challenging, but a licensed professional should perform the part of the installation that involves connecting gas lines or supplying electrical service to the heater unit. Likewise, the plumbing connections require at least moderate expertise in soldering and sweating joints for supplying water service under pressure.

References

• Tankless Water Heater FAQs
• How to Install an Instantaneous Water Heater