How to Install a Tankless Water Heater. Tankless water heaters (sometimes called on-demand water heaters or instantaneous water heaters) have been a staple in Europe and Asia for quite a few years, and they are now becoming more common in North America. Tankless heaters are electric or gas powered heaters that don't have a storage tank (like the vast majority of water heaters we are used to). Instead, the tankless heater has a water pressure sensor that recognizes when you turn on the hot water tap. Cold water flows through a grid in the heater where it is quickly heated and then flows to your tap. When you shut off the water, the heating element shuts down until the next time. Manufacturers claim you can get energy savings of 20 to 30% in homes using tankless heaters.
Choosing a System
Tankless systems are available as single central systems (to essentially replace the hot water storage tank), or as smaller units that can be installed near where the hot water demand takes place (close to a washing machine for example).
Consider how your family uses hot water. A faucet typically uses .75 gallons per minute (gpm) while a washing machine or dishwasher uses approximately 2.0 gpm. If more than one of you showers at the same time or you wash clothes and dishes at the same time, you will need a tankless heater that can produce enough to keep up with your hot water demands.
Determine what you want the heater to do. Is it to serve as a supplemental heater for a single bathroom or as a total replacement for your existing storage tank system?
Understand how tankless water heaters are sized. The heaters are sized based on their ability to provide hot water at a given flow rate (gpm) plus the temperature increase they can produce. If your incoming water temperature is 50 degrees and you want your hot water to be 120 degrees, your system needs to be able to raise the temperature 70 degrees while maintaining your needed flow rate.
Installing a Tankless Water Heating System
Manufacturer's recommend you have a qualified contractor install your water heater. The tankless systems require a lot of energy when they are operating and most existing homes are not capable of supporting them without modifications and upgrades to their electrical or gas systems.
Installation of a dedicated circuit is a minimum requirement for electric tankless systems. Heavier gauge wiring for the circuit to the tankless heater is also commonly recommended.
Modification to existing gas venting systems is often necessary to meet the demands of the gas heaters used in tankless systems.