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Table 1
Natural Gas Pipe Capacity Table (Cu. Ft./Hr.)
Capacity of gas pipe of different diameters and lengths in cu. ft. per hr.
of 0.60 (natural gas).
with pressure drop of 0.3 in. and specific gravity
Nominallron Pipe Length ofPipe, Feet
Size,in. 10 20 30 40 50 60 70 80 90 100 125 150 175 200
1/2 132 92 73 63 56 50 46 43 40 38 34 31 28 26
3_ 278 190 152 130 115 105 96 90 84 79 72 64 59 55
1 520 350 285 245 215 195 180 170 160 150 130 120 110 100
1-1_ 1050 730 590 500 440 400 370 350 320 305 275 250 225 210
1-1/2 1600 1100 890 760 670 610 560 530 490 460 410 380 350 320
After the lengthof pipe has been determined,select the pipe sizewhich will provide theminimum cubic feet perhour
requiredfor the gas inputrating of the water heater. Byformula:
Gas Input of Water Heater (BTU/HR)
Cu. Ft. Per Hr. Required=
Heating Value of Gas (BTU/FT 3)
The gas input of the water heater is marked on the water heater data plate. The heating value of the gas (BTU/FT _)
may be determined by consulting the local natural gas utility.
Table 2
LP Gas Capacity Table
Maximum capacity of pipe in thousands of BTU per hour of undiluted liquefied petroleum gases (at 11 inches water
column pressure). Based on a pressure drop of 0.5 inch water column.
Nominal Iron Pipe Length of Pipe, Feet
Size, in. I 0 20 30 40 50 60 70 80 90 I O0 125 150
1/2 275 189 152 129 114 103 96 89 83 78 69 63
3/4 576 393 315 267 237 217 196 185 173 162 146 132
1 1071 732 590 504 448 409 378 346 322 307 275 252
1-1/4 2205 1496 1212 1039 913 834 771 724 677 630 567 511
Example: Input BTU requirement of the water heater 100,000 BTU/HR.
Total pipe length, 80 feet = 3/4" IPS required.
Additional tables are available in the latest edition of the "National Fuel Gas Code", ANSI Z223.1.
Combustion Air Supply and
Ventilation
Carbon Monoxide Hazard
Water heater must be vented to outdoors.
Vent must be installed by a qualified person
using the installation instructions.
Examples of a qualified person include:
gas technicians,
authorized gas company personnel,
and authorized service persons.
Failure to follow these instructions can result
in death or carbon monoxide poisoning.
IMPORTANT: Air for combustion and ventilation must
not come from a corrosive atmosphere. Any failure due
to corrosive elements in the atmosphere is excluded from
warranty coverage.
The following types of installation (not limited to the
following) will require outdoor air for combustion due to
chemical exposure and may reduce but not eliminate the
presence of corrosive chemicals in the air:
• beauty shops
• photo processing labs
• buildings with indoor pools
• water heaters installed in laundry, hobby, or craft rooms
• water heaters installed near chemical storage areas
Combustion air must be free of acid-forming chemicals
such as sulfur, fluorine, and chlorine. These elements are
found in aerosol sprays, detergents, bleaches, cleaning
solvents, air fresheners, paint, and varnish removers,
refrigerants, and many other commercial and household
products. When burned, vapors from these products form
highly corrosive acid compounds. These products should
not be stored or used near the water heater or air inlet.
Combustion and ventilation air requirements are
determined by the location of the water heater. The water
heater may be located in either an open (unconfined) area
or in a confined area or small enclosure such as a closet or
small room. Confined spaces are areas with less than 50
cubic feet for each 1,000 BTU/HR of the total input for all
gas-using appliances.
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