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Gas Supply Piping
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 190,000 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 “Tee” to the actual
length. Use the charts below to determine the pipe
diameter necessary to accommodate the BTU
demand of the unit. If there are more than one 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 2.6”
WC for natural gas, and 3.4” 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