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 pan constructed of one of the following:
- Galvanized steel or aluminum of not less than 0.0236 inch (0.6010 mm) in thickness.
- Plastic not less than 0.036 inch (0.9 mm) in thickness.
- Other approved materials.
A plastic pan shall not be installed beneath a gas-fired water heater.
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.
The discharge piping serving a pressure-relief valve, temperature relief valve or combination valve shall:
- Not be directly connected to the drainage system.
- Discharge through an air gap located in the same room as the water heater.
- Not be smaller than the diameter of the outlet of the valve served and shall discharge full size to the air gap.
- Serve a single relief device and shall not connect to piping serving any other relief device or equipment.
- Discharge to the floor, to the pan serving the water heater or storage tank, to a waste receptor or to the outdoors.
- Discharge in a manner that does not cause personal injury or structural damage.
- Discharge to a termination point that is readily observable by the building occupants.
- Not be trapped.
- Be installed to flow by gravity.
- Terminate not more than 6 inches (152 mm) and not less than two times the discharge pipe diameter above the floor or waste receptor flood level rim.
- Not have a threaded connection at the end of the piping.
- Not have valves or tee fittings.
- Be constructed of those materials indicated in Section P2906.5 or materials tested, rated and approved for such use in accordance with ASME A112.4.1.
- Be one nominal size larger than the size of the relief-valve outlet, where the relief-valve discharge piping is constructed of PEX or PE-RT tubing. The outlet end of such tubing shall be fastened in place.