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Gas Piping
Chapter 4. – Installation
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 on page 25)
• 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 on page 25).
• For all LP installation use. (Table 3 on page 25)
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.
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
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). It is not recommended to pressure
test 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 (NFPA54), 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 Btu/h demand of the building and length
from the meter or regulator so that the following supply pressures are available even at maximum demand.
CAUTION
Natural Gas Supply Pressure
Min 3.5" WC
Max 10.5" WC
LP Gas Supply Pressure
Min 8" WC
Max 14" WC
Reference Tools & Sample Calculations
