SBN71-120 thru 85-390, SBD30-150/199 TANK TYPE COMMERCIAL
GAS WATER HEATER SERVICE HANDBOOK
COMBINED VENTING
COMBINING VENTS (MANIFOLDING
When vents are combined, the area of the combined vent should be equal to area of the largest single vent, plus 50% of area of all others joining.
EXAMPLE: To combine two 6” vents with an 8” vent, the area of a combined vent should be one half area of two 6 inch vents (14 + 14) plus area of 8 inch vent (50)
or 78 sq. inches.
Referring to chart: 78 sq. inches requires a 10” diameter vent.
Vent Size | Area in | Vent Size | Area in |
| Square |
| Square |
| Inches |
| Inches |
5" | 20 | 10" | 79 |
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6" | 28 | 12" | 113 |
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|
7" | 38 | 14" | 154 |
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8" | 50 | 16" | 201 |
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9" | 64 | 18" | 254 |
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Maximize height from water heater vent connection to first elbow or tee.
State Water Heaters | 19 | Technical Training Department |
Ashland City, Tennessee © 2007 |
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