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Gas Lines to Tankless Water Heaters

If you are replacing an existing water heater or considering installing a tankless unit, it’s important to know what size gas line your home requires. A typical tankless water heater will need a ¾-inch gas line. However, if there is sufficient pressure and the run length is short enough, a ½-inch line may be sufficient with certain tankless water heaters, such as the Noritz EZ Series.

An on demand or “tankless” water heater is meant to provide hot water only as needed without the standby loss of energy associated with traditional tank units. The more common type of gas on demand hot water heater is known as an indirect fired unit that uses natural gas or propane fuel to generate the necessary energy required for operation.

Disclaimer: This article is for informational purposes only and does not cover every situation. Your local building codes supersede the guidance in this article. Please consult your local building officials for any additional requirements or restrictions in your area before installing a new water heater, gas line to tankless water heater, or venting system.

What size gas line is required?

A typical tankless water heater will need a ¾-inch gas line. It’s important to use the proper diameter piping when sizing the gas line to your unit because using pipe that’s too large can result in lower than desired BTU’s (British Thermal Units) which may lead to poor heating performance when you try to heat water for hot showers or running appliances such as dishwashers or washing machines.

Similarly, using pipe that’s too small can result in insufficient flow and the same issues mentioned above. There may also be an issue with gas pressure. If you end up needing to use pipe that’s smaller than ¾-inch you will have to have your gas supplier check your line for sufficient pressure before installing the water heater.

The best way to ensure proper sizing is to call a local plumber who specializes in gas lines before purchasing your tankless water heater if you are unable to obtain specs from the manufacturer of the unit you have selected. The plumber should have no problem getting this information or at least advising if it’s necessary for them to come out themselves and your home prior to purchase.

What else do I need?

In addition to a gas line, tankless water heaters also require adequate combustion air and a vent to remove combustion gas. You will also need an electrical outlet if you plan on using a “power-vent” type of unit. This is because the fan that ejects the burnt combustion gases out of your home needs electricity in order for it function properly.

Prices for installation can vary significantly from as little as $400 up to as much as $1,000 or more depending upon your location and the type of unit you decide upon. In all cases, make sure to ask any company you are considering doing business with about installation costs before making any decisions. Always check references and be careful not to go with the lowest bidder.

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