2009 IRC change highlighted below:
"P2803.6.1 Requirements for discharge pipe. 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
- 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. **
- 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.
- Not terminate more than 6 inches (152 mm) above
the floor or waste receptor.
- Not have a threaded connection at the end of the piping.
- Not have valves or tee fittings.
- Be constructed of those materials listed in Section
P2904.5 or materials tested, rated and approved for
such use in accordance with ASME A112.4.1. 438"