9
Pressure Test
The appliance and its gas connections must be leak tested before placing the appliance in operation.
The appliance must be isolated from the gas supply piping system by closing its individual manual
shutoff valve during any pressure testing of the gas supply piping system at test pressures equal to
or less than ½ psig (3.5 kPa). We do not recommend pressure testing in excess of ½ psig (3.5kPa).
If it must be done, the appliance and its individual shutoff valve must be completely disconnected
from the gas supply piping system during the test process.
Pipe Sizing/Flexible Connectors
A gas shutoff valve must be installed on the supply line. Gas flex lines are not recommended unless
the minimum inside diameter is ¾” or greater and the rated capacity of the connector is equal to
or greater than the BTU capacity of the water heater. Gas piping shall be in accordance with local
utility company requirements and/or in the absence of local codes, use the latest edition of National
Fuel Gas Code (NFPA54GC), ANSI Z223.1. In Canada, use the latest edition of CSA B149.1, National
Gas and Propane installation code. Size the gas line according to total btuh demand of the building
and length from the meter or regulator so that the following supply pressures are available even at
maximum demand.
WARNING
Natural Gas Supply Pressure
Min 4” WC
Max 10.5” WC
LP Gas Supply Pressure
Min 8” WC
Max 14” WC
Reference Tools & Sample Calculations
The tables and samples below are for reference only. The professional sizing and installing the gas
line should always run the appropriate calculations before all installations.
CAUTION
Which Table to Use
• For NG installations with the initial supply pressure at point of delivery (at the meter, for example) is
less than 8” WC, use the 0.5” WC pressure drop table (Table 1).
• For NG installations with the initial supply pressure at point of delivery is greater than or equal to 8”
WC, use the 3.0” pressure drop table (Table 2).
• For all LP installation use (Table 3)
The inlet pressure must be at least 5” WC for NG or 8” WC for LP for all appliances in the gas system.
If the inlet gas pressure drops below 5” WC for NG or 8” WC for LP, the heater may continue to operate,
but the other appliances in the house may experience flame loss or ignition failure, which can result in
gas leakage into the home. Refer to the NFPA 54 for details.
Please contact Noritz for details. For corrugated stainless steel tubing (CSST) capacity tables, please
consult with the manufacturer.