In 248 CMR section 10.12 (1) (h) Safe Waste Required, it states:
Safe Waste Required.
1. A safe waste pan shall be installed under water heaters or hot water storage tanks that are six (6) gallons in capacity or larger and are installed in a position elevated above any occupied space.
2. The safe waste pan shall be installed under water heaters and hot water storage tanks where there is occupancy below and shall be piped indirectly to a properly trapped and vented fixture.
When installing a replacement water heater or hot water storage tank that is in a position elevated above any occupied space, it may not be practical to install a safe waste pan.
When installing a replacement water heater or hot water storage tank and it is not practical to install a safe waste pan and related safe waste drain piping, an acceptable alternate method to satisfy the requirements of 248 CMR 10.12 (1) (h) may be to install a product approved automatic water heater shut off device and a safe waste pan without the related drain piping.
If this method is used, the water heater temperature and pressure relief valve shall discharge into the water heater safe waste pan.