How to Install a Tankless Water Heater

One of the most common request we hear during an inspection is “I’d like to change my tank style water heater to a tankless model.”  Tankless water heaters are a compact and efficient way to supply hot water. The guys at This Old House explain a few steps required for a typical gas tankless water heater installation.

Depending on the model gas heater you chose it may be required to change the type, size and style vent. That could mean a larger hole in your roof with a larger or different material vent flashing.

It’s very common that the existing gas line be increased in size. Take special care if your plumber installs a flexible type gas service line. The line, called corrugated stainless steel tubing or CSST, will require bonding to reduce the possibility of CSST lightning damage:

1) Yellow-jacketed CSST should be bonded (connected to the electrical service panel’s ground bus) at its entrance into a building. Many local codes require this.

2) All CSST should be installed away from metal objects such as metal duct work, metal pipes, electrical wiring, metal beams, or metal conduit.

All tankless models require power. Electricity will need to be installed at the new or existing location. If you don’t already have work space lighting near the heater, now is a great time to install new lighting. Tankless models require regular maintenance and the lighting will come in handy. I suggest you install a fixture with a protective globe in the work zone.

One of the most critical mistakes are made when thinking any tankless heater will replace your standard 40 Gal heater. The new tankless model will be sized based on incoming water temp, how many points of use in the hone and how far from the points of use the tank is located. Here are some basic sizing guidelines from Takagi.

Don’t forget to check with your local building department and ask about plumbing and electrical permitting. For those reasons we highly recommend the heater be installed by a professional.

The video briefly explains the advantages of installing a high efficiency condensating heater. I recommend upgrading to a condensating heater.

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2 thoughts on “How to Install a Tankless Water Heater

  1. I’ll be removing my old water heater and installing a new one as mine isn’t working all that well. I’ll be going the tankless route since they are more compact and efficient. As you said, I should make sure that the existing gas like will work for it since it may need to be changed in size.

  2. Thanks for the heater installation tips. I would like to get a heater installed in my own home. It is currently going through some renovations, and I think now is the right time to have heating professionally installed.

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