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Heater Pans

2003 IRC P2801.5 Required Pan. Where water heaters or hot water storage tanks are installed in locations where leakage of the tanks or connections will cause damage, the tank or water heater shall be installed in a galvanized steel pan having a minimum thickness of 24 gage (0.016") (0.4 mm) or other pans for such use. Listed pans shall comply with CSA LC3.

It also goes on to say the pan will be drained by an indirect waste pipe having a minimum diameter of 3/4". It's a good idea to write up second floor or attic water heaters that do not have pans or have damaged pans. It's a judgment call on first floor heaters, i.e. is there really a risk of collateral damage from a leak? If so, then write it up.

The 2003 IRC may or may not be applicable to your area. You need to know what your state/AHJ has adopted.