The right size is a tankless water heater that can heat enough gallons of water to a specific temperature per minute to keep up with the demand.
Tankless water heater gas supply line size.
Branch 1 e tankless water heater 199 900 20 ft 1 g gas furnace 75 000 15 ft d branch main line 274 900 30 ft 1 branch 2 j gas dryer 25 000 20 ft h gas range 55 000 30 ft k gas logs 40 000 10 ft b c branch main line 120 000 45 ft main trunk a main trunk line 394 900 20 ft 1.
Typically the gas piping has to be upgraded to support the tankless water heater due to the volume of fuel that is required.
Tables 2 and 3 provide the capacity by pipe size and length based on the maximum allowable pressure drops.
Like a hot water tank for 5 people will require at least a 60 gallon tank.
Rinnai tankless water heaters are designed to provide maximum performance and efficiency using either a 3 4 or 1 2 gas line as long as sufficient gas flow is available.
Gallons per minute gpm is the key when it comes to sizing tankless water heaters.
Since tankless water heaters supply endless hot water you don t have to worry about capacity but instead think in terms of water flow rate.
In all cases a near 200 000 btu gas appliance will require a minimum of a inch gas supply line.