Gas Supply Piping
Attention: Proper gas pressure is important but gas
volume is more critical than pressure. Right volume gas
supplies to system can be expect full performance. You
may calculate right gas pipe for right volume supply.
Check the rating plate to make sure that the unit was
built for the type of gas available in the area.
The gas supply piping should be sized according to the
Applicable Plumbing Code for a maximum draw of
185,000 BTUH. First determine the effective length of
the gas supply line by measuring the actual length of
piping, and then adding 5 ft. for every elbow or “T” to
the actual length. Use the charts below to determine
the pipe diameter necessary to accommodate the BTU
demand of the unit. If there is more gas drawing
appliances on the line, size according to the maximum
amount of BTU demand.
The gas supply pressures must be within the ranges of
the following chart:
Natural Gas
Supply Pressure
Min. 5” WC
Max. 10.5” WC
Propane Gas
Supply Pressure
Min. 11” WC
Max. 14” WC
Insufficient gas supply pressure can cause the Flash
Water Heater to lose efficiency or not work at all.
WARNING: Fire or explosion may result if the maximum
supply pressures are exceeded.
The manifold gas pressure should be at maximum 2.3”
WC for natural gas, and 2.5” WC for propane.
Always use approved connectors to connect the unit to
the gas line. Always purge the gas line of any debris
before connecting to the water heater.
WARNING: Conversion of this unit from natural gas to
propane or propane to natural gas cannot be done in
the field. Contact your local retailer or distributor to get
the correct unit for your gas type.
Always install a manual shutoff valve on the gas supply
line in case of an emergency, or if service or
maintenance is necessary.
This appliance and its individual shut-off valve must be
isolated from the gas supply piping system by
unplugging the unit and turning off the main gas valve
during any pressure testing of the gas supply piping
system at test pressures equal to or less than ½ PSI.
When all of the connections have been made, check
the gas line for leaks. Apply soapy water to all gas
fittings and connections, if bubbles form, there may be a
leak.
Natural Gas Supply Piping
Based on 0.60 specific gravity for natural gas at .5” WC pressure drop
DOE standard is 1100 BTU per cubic ft. of natural gas
Pipe
Size
Cubic Feet of Natural Gas
Length 10’ 20’ 30’ 40’ 50’ 60’ 70’ 80’ 90’ 100’ 125’ 150’ 200’
½” 174 119 96 82 73 66 61 56 53 50 44 40 34
¾” 363 249 200 171 152 138 127 118 111 104 93 84 72
1” 684 470 377 323 286 259 239 222 208 197 174 158 135
1 ¼” 1404 965 775 663 588 532 490 456 428 404 358 324 278
1 ½” 2103 1445 1161 993 880 798 734 683 641 605 536 486 416
2” 4050 2784 2235 1913 1696 1536 1413 1315 1234 1165 1033 936 801
Propane Supply Piping
Based on 11” WC supply pressure
Pipe
Size
kBTU of Propane
Length 10’ 20’ 30’ 40’ 50’ 60’ 70’ 80’ 90’ 100’ 125’ 150’ 200’
½” 275 189 152 129 114 103 96 89 83 78 69 63 55
¾” 567 393 315 267 237 217 196 185 173 162 146 132 112
1” 1071 732 590 504 448 409 378 346 322 307 275 252 213
1 ¼” 2205 1496 1212 1039 913 834 771 724 677 630 567 511 440
1 ½” 3307 2299 1858 1559 1417 1275 1181 1086 1023 976 866 787 675
2” 6221 4331 3465 2992 2646 2394 2205 2047 1921 1811 1606 1496 1260
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