CHAPTER 28
WATER HEATERS


  • SECTION P2801
    GENERAL

    P2801.1 Required.
    Each dwelling shall have an approved automatic water heater or other type of domestic water-heating system sufficient to supply hot water to plumbing fixtures and appliances intended for bathing, washing or culinary purposes. Storage tanks shall be constructed of noncorrosive metal or shall be lined with noncorrosive material.

    P2801.2 Installation.
    Water heaters shall be installed in accordance with this chapter and Chapters 20 and 24.

    P2801.3 Location.
    Water heaters and storage tanks shall be installed in accordance with Section M1305 and shall be located and connected to provide access for observation, maintenance, servicing and replacement.

    P2801.4 Prohibited locations.
    Water heaters shall be located in accordance with Chapter 20.

    P2801.5 Required pan.
    Where a storage tank-type water heater or a hot water storage tank is installed in a location where water leakage from the tank will cause damage, the tank shall be installed in a galvanized steel pan having a material thickness of not less than 0.0236 inch (0.6010 mm) (No. 24 gage), or other pans approved for such use. Listed pans shall comply with CSA LC3.

    P2801.5.1 Pan size and drain.
    The pan shall be not less than 11/2 inches (38 mm) deep and shall be of sufficient size and shape to receive all dripping or condensate from the tank or water heater. The pan shall be drained by an indirect waste pipe of not less than 3/4 inch (19 mm) diameter. Piping for safety pan drains shall be of those materials listed in Table P2905.5.

    P2801.5.2 Pan drain termination.
    The pan drain shall extend full-size and terminate over a suitably located indirect waste receptor or shall extend to the exterior of the building and terminate not less than 6 inches (152 mm) and not more than 24 inches (610 mm) above the adjacent ground surface.

    P2801.6 Water heaters installed in garages.
    Water heaters having an ignition source shall be elevated such that the source of ignition is not less than 18 inches (457 mm) above the garage floor.

    Exception: Elevation of the ignition source is not required for appliances that are listed as flammable vapor ignition-resistant.

    P2801.7 Water heater seismic bracing.
    In Seismic Design Categories D0, D1 and D2 and townhouses in Seismic Design Category C, water heaters shall be anchored or strapped in the upper one-third and in the lower one-third of the appliance to resist a horizontal force equal to one-third of the operating weight of the water heater, acting in any horizontal direction, or in accordance with the appliance manufacturer’s recommendations.

    SECTION P2802
    WATER HEATERS USED FOR SPACE HEATING

    P2802.1 Protection of potable water.
    Piping and components connected to a water heater for space heating applications shall be suitable for use with potable water in accordance with Chapter 29. Water heaters that will be used to supply potable water shall not be connected to a heating system or components previously used with nonpotable-water heating appliances. Chemicals for boiler treatment shall not be introduced into the water heater.

    P2802.2 Temperature control.
    Where a combination water heater-space heating system requires water for space heating at temperatures exceeding 140°F (60°C), a master thermostatic mixing valve complying with ASSE 1017 shall be installed to temper the water to a temperature of not greater than 140°F (60°C) for domestic uses.

    SECTION P2803
    RELIEF VALVES

    P2803.1 Relief valves required.
    Appliances and equipment used for heating water or storing hot water shall be protected by:

    1. A separate pressure-relief valve and a separate temperature-relief valve; or

    2. A combination pressure- and temperature-relief valve.

    P2803.2 Rating.
    Relief valves shall have a minimum rated capacity for the equipment served and shall conform to ANSI Z21.22.

    P2803.3 Pressure-relief valves.
    Pressure-relief valves shall have a relief rating adequate to meet the pressure conditions for the appliances or equipment protected. In tanks, they shall be installed directly into a tank tapping or in a water line close to the tank. They shall be set to open at not less than 25 psi (172 kPa) above the system pressure but not over 150 psi (1034 kPa). The relief-valve setting shall not exceed the tanks rated working pressure.

    P2803.4 Temperature-relief valves.
    Temperature-relief valves shall have a relief rating compatible with the temperature conditions of the appliances or equipment protected. The valves shall be installed such that the temperature-sensing element monitors the water within the top 6 inches (152 mm) of the tank. The valve shall be set to open at a temperature of not greater than 210°F (99°C).

    P2803.5 Combination pressure-/temperature-relief valves.
    Combination pressure-/temperature-relief valves shall comply with all the requirements for separate pressure- and temperature-relief valves.

    P2803.6 Installation of relief valves.
    A check or shutoff valve shall not be installed in the following locations:

    1. Between a relief valve and the termination point of the relief valve discharge pipe;

    2. Between a relief valve and a tank; or

    3. Between a relief valve and heating appliances or equipment.

    P2803.6.1 Requirements for discharge pipe.
    The discharge piping serving a pressure-relief valve, temperature-relief valve or combination valve shall:

    1. Not be directly connected to the drainage system.

    2. Discharge through an air gap located in the same room as the water heater.

    3. Not be smaller than the diameter of the outlet of the valve served and shall discharge full size to the air gap.

    4. Serve a single relief device and shall not connect to piping serving any other relief device or equipment.

    5. Discharge to the floor, to the pan serving the water heater or storage tank, to a waste receptor or to the outdoors.

    6. Discharge in a manner that does not cause personal injury or structural damage.

    7. Discharge to a termination point that is readily observable by the building occupants.

    8. Not be trapped.

    9. Be installed to flow by gravity.

    10. Not terminate more than 6 inches (152 mm) above the floor or waste receptor.

    11. Not have a threaded connection at the end of the piping.

    12. Not have valves or tee fittings.

    13. Be constructed of those materials listed in Section P2905.5 or materials tested, rated and approved for such use in accordance with ASME A112.4.1.

    P2803.7 Vacuum-relief valve.
    Bottom fed tank-type water heaters and bottom fed tanks connected to water heaters shall have a vacuum-relief valve installed that complies with ANSI Z21.22.