What size gas line does a Rinnai tankless water heater require?
The gas connection on the unit is ¾” MNPT, but that does not mean that is the size your gas line should be. The gas supply should be sized to handle the total load of all appliances at your location. The Rinnai tankless water heater will add up to 199,000 BTU’s per heater installed at the location. Gas line sizing should be performed by the professionals installing your appliances. There is no way Rinnai can size your gas supply lines without detailed drawings showing the meter, regulators, sizes of these fixtures, and length of pipe from the meter to each appliance, and the BTU value of each appliance. Rinnai recommends that you contact your gas provider for accurate sizing.