504.6 Requirements for discharge piping. The discharge
piping serving a pressure relief valve, temperature relief valve
or combination thereof 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 pip-
ing serving any other relief device or equipment.
5. Discharge to the floor, to an indirect waste receptor or
to the outdoors. Where discharging to the outdoors in
areas subject to freezing, discharge piping shall be first
piped to an indirect waste receptor through an air gap
located in a conditioned area.
6. Discharge in a manner that does not cause personal
injury or structural damage.
7. Discharge- to a termination point that is readily observ-
able by the building occupants.
8. Not be trapped.
9. Be installed so as to flow by gravity.
10. Not terminate more than 6 inches (152 mm) above the
floor or waste receptor.
1 1 . Not have a threaded connection at the end of such pip-
12. Not have valves or tee fittings.
13. Be constructed of those materials listed in Section
605.4 or materials tested, rated and approved for such
use in accordance with ASME Al 12.4.1.