If there is no large, cylindrical hot water storage tank in your home, chances are that you have a tankless water heater. Although they are often more expensive than tank-type water heaters, there are many advantages to going tankless. Also known as instantaneous or on-demand water heaters, tankless systems only produce hot water when you need it, and they do so with close to zero lag time. Tankless water heaters often save homeowners money because they only heat water as it’s being used as opposed to continuously using energy to keep a tank of water warm throughout the day. Like a pay-as-you-go plan, you only pay for the hot water you use. Because tankless water heaters don’t require as much maintenance and can last up to 25 years, they usually pay for themselves. They also take up far less space than a tank-type water heater.
Another difference with tankless water heaters is that they produce water at a much hotter temperature since it’s coming directly from the heating element instead of a holding tank. For this reason, we recommend that a thermostatic mixing valve be installed to prevent scalding.
As mentioned above, gas-fired tankless water heaters only heat up water when you need it. How does this work? When you turn on a hot water valve or an appliance that draws hot water such as a washing machine or dishwasher, the gas-fired tankless water heater will draw cold water in through the cold-water inlet pipe on one side. The cold water flowing into the system hits a flow sensor inside the unit that relays a signal to the computer within the water heater. The computer pulls in gas and ignites a fire within the contained burner, which provides heat to the heat exchanger. The incoming water is then circulated through the activated heat exchanger, heating the water to the temperature set on the thermostat before leaving the system through the hot water outlet pipe where it is directed to the appropriate faucet or appliance. This all happens within seconds, effectively giving homeowners instant access to hot water. When there is no demand for hot water, the system shuts itself off.
Similar to gas-fired tank-type systems, gas-fired tankless systems include a vent that removes any by-products created during the combustion process. A small fan underneath the burner propels the by-products up through the vent, where they are carried outside of the home.
Point-of-use units are used to quickly supply hot water to a source not located near the home’s central water heater. These units are not intended to replace a water heater, but instead are luxury add-ons to a home with a functioning water heater. Much like whole-home tankless water heaters, point-of-use units don’t have to keep a tank of water warm and only operate when hot water is in use.
Circulation pumps are also used to supply warm water more quickly to a source as you use it. The difference between point-of-use units and circulation pumps is that a point-of-use unit heats water at the source, while a circulation pump keeps warm water flowing through your home and back to the water heater so that there is a constant stream of warm water passing through your home’s pipes.