GAS WATER HEATER SIZING GUIDE
Use the following information as a guide to approximate the correct size water heater for the residence:
•40 gallon size (28 gallon draw) for two bath residence
•50 gallon size (35 gallon draw) for three bath residence - or two baths with an automatic clothes washer.
•When a whirlpool tub is part of the home equipment, it is suggested that the water heater storage tank capacity be selected based on the needs of the whirlpool tub. This method of tank sizing, will in most cases, cancel all statements above concerning tank sizing.
•High flow or multiple shower head installations must be sized for at least a 20 minute draw.
Table 2:
Tub Capacity to Overflow | 80 gal. | 90 gal. | 100 gal. | 110 gal. | 120 gal. | 130 gal. | 140 gal. | 150 gal. | |
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(120ºF Water) Min. Stored | 80 gal. | 90 gal. | 100 gal. | 110 gal. | 120 gal. | 130 gal. | 140 gal. | 150 gal. | |
Water Capacity** | |||||||||
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(140ºF Water*) Min. Stored | 65 gal. | 71 gal. | 80 gal. | 89 gal. | 98 gal. | 108 gal. | 117 gal. | 125 gal. | |
Water Capacity** | |||||||||
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(@ 160ºF Water*) Min. | 54 gal. | 59 gal. | 66 gal. | 74 gal. | 82 gal. | 90 gal. | 97 gal. | 104 gal. | |
Stored Water Capacity** | |||||||||
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*A thermostatic mixing valve set for a maximum temperature of 120° F is recommended to be installed to prevent a scalding hazard.
**Based on tub water temperature of 105º
Note: Because the desired fill time is normally 10 minutes, recovery capacity is not used for this calculation. All water used is supplied by storage.
NOTE: The draw efficiency of a gas or electric water heater storage tank is considered to be 70%.
LEAKAGE CHECKPOINTS
A. | Water at the draft hood is water vapor which has | * To check where threaded portion enters tank, | |
| condensed out of the combustion products. This is | insert cotton swab between jacket opening and | |
| caused by a problem in the vent. | fitting. If cotton is wet, follow draining instructions | |
B. | *Condensation may be seen on pipes in humid | in the “Draining the Water Heater” section and then | |
| weather or pipe connections may be leaking. | remove fitting. Put pipe dope or Teflon® tape on the | |
C. | *The powered anode rod fitting may be leaking. | threads and replace. When you are finished, follow | |
D. | Small amounts of water from | the steps in “Filling the Water Heater” section. | |
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| relief valve may be due to thermal expansion or | A | C |
| high water pressure in your area. | B | |
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E. | *The |
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| leaking at the tank fitting. |
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F. | Water from a drain valve may be due to the valve |
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| being slightly opened. |
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G. | *The drain valve may be leaking at the tank fitting. | D |
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H. | Combustion products contain water vapor which |
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| can condense on the cooler surfaces of the tank. |
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| Droplets form and drip onto the burner or run on |
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| the floor. This is common at the time of |
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| after installation and when incoming water is cold. | G |
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I. | Water in the water heater bottom or on the floor |
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| may be from condensation, loose connections, or |
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| the relief valve. DO NOT replace the water heater |
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| until a full inspection of all possible water sources | F | I |
| is made and necessary corrective steps taken. | ||
| 6” (152.4 mm) |
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Leakage from other appliances, water lines, or ground | MAXIMUM AIR GAP |
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seepage should also be checked. | Figure 122 |
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