Article and photos by Gregory Havel
Domestic water heaters were originally part of cast-iron cooking stoves. Someone had to carry water from the well and keep the reservoir filled. When hot water was needed, it was dipped from the reservoir, unless the reservoir had a tap on the side.
When heating boilers became common, domestic water heaters were made a part of them, with water under pressure piped to it from a storage tank, and from the water heater to indoor plumbing fixtures. Domestic water heaters as separate appliances became common when wartime petroleum rationing made it difficult to operate the heating boiler year round for hot water.
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Photo 1 shows a pair of conventional water heaters; each combines a heating unit and a storage tank. They are in a large house, with looped hot water piping and circulating pumps to make hot water available at any plumbing fixture at any time. These are modern units, with sealed combustion chambers, electronic ignition, electrically operated dampers, high-efficiency burners, and PVC (plastic) vent and combustion air pipes. Domestic water heaters in commercial and industrial buildings use similar appliances and arrangements, but can they may use larger, or a greater number of, appliances.
With today’s high energy costs and the effect of energy conservation regulations on plumbing codes, manufacturers have found more ways to reduce energy consumption, in addition to using electronic ignition and sealed combustion chambers.
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Photo 2 shows a pair of gas-fueled “tankless” or “point-of-use” water heaters. In addition to fuel piping, they also need an electric circuit to operate the electronic ignition and microprocessor controls. In residential and commercial buildings where these units are used, the cold water and natural gas are piped to the water heater location near each group of plumbing fixtures. The water heater keeps only a small amount of water (a quart or 0.9 liter) warm and rapidly heats more water as it is used when a faucet is opened. Little energy is used in keeping the small amount of stored water warm, and most of the energy is used only when hot water is needed. These appliances use sealed combustion chambers and have flue gas temperatures low enough so that both air supply and vent piping are usually made of Schedule 40 PVC pipe. Since the flue gas temperature is often below its dew point, a trap and drain are provided to remove the condensed moisture (shown on the right below each water heater). All-electric models that do not need fuel or condensation drains are also available. .
When you are doing primary search in a building or investigating a report of a gas leak or a carbon monoxide alarm, be aware that the water heaters may not look like traditional appliances and that they may be located anywhere: in closets, inside cabinets, in the basement, or in the attic. Remember that just because you have found one of them does not mean that you have found the only one.
Another significant point in developing prefire plans, as well as strategy and tactics for an incident, is that in a modern building, it is less expensive to build and more energy-efficient to operate when we pipe the fuel (natural gas) throughout the building, so that the energy will be used only where it is needed. Fuel is likely to be piped throughout the building to appliances, instead of only to the boiler or utility room and kitchen.
Even more common that the state-of-the-art water heaters shown in these photos are the basic 30- and 40-gallon vertical white water heaters that have been in use since the 1950s. Since there are millions of these still in service, and since these are still available for new and replacement installations in many parts of North America, they will be discussed in a future article.
Following are suggestions for obtaining additional information on modern water heaters and fuel efficiency:
- Visit the Web site of your local electric and natural gas utilities
- Search the Internet for “water heater” and “tankless water heater.”
- Consult NFPA 54, National Fuel Gas Code.
- Consult NFPA 85, Boiler and Combustion Systems Hazards Code.
- Visit the manufacturers’ Web sites for brands of water heaters with which you are familiar.
- Visit a local home improvement store for displays and literature.
- Discuss your state and local codes and plumbing and energy-efficiency requirements with your local building inspector or a licensed plumber.
Gregory Havel is a member of the Burlington (WI) Fire Department; a retired deputy chief and training officer; and a 30-year veteran of the fire service. He is a Wisconsin-certified fire instructor II and fire officer II, an adjunct instructor in fire service programs at Gateway Technical College, and safety director for Scherrer Construction Co., Inc. Havel has a bachelor’s degree from St. Norbert College; has more than 30 years of experience in facilities management and building construction; and has presented classes at FDIC
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Subjects: Building construction for firefighters, water heaters
