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TPR drain interconnected with drain pan's drain

Trent Tarter

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504.6 Requirements for discharge piping.

The discharge piping serving a pressure relief valve, temperature relief valve or combination thereof shall:

  1. 1.Not be directly connected to the drainage system.

  2. 2.Discharge through an air gap located in the same room as the water heater.

  3. 3.Not be smaller than the diameter of the outlet of the valve served and shall discharge full size to the air gap.

  4. 4 Serve a single relief device and shall not connect to piping serving any other relief device or equipment.

  5. 5.Discharge to the floor, to the pan serving the water heater or storage tank, to a waste receptor or to the outdoors.

  6. 6.Discharge in a manner that does not cause personal injury or structural damage.

  7. 7.Discharge to a termination point that is readily observable by the building occupants.

  8. 8.Not be trapped.

  9. 9.Be installed so as to flow by gravity.

  10. 10.Terminate not more than 6 inches (152 mm) above and not less than two times the discharge pipe diameter above the floor or flood level rim of the waste receptor.

  11. 11.Not have a threaded connection at the end of such piping.

  12. 12.Not have valves or tee fittings.

  13. 13.Be constructed of those materials listed in Section 605.4 or materials tested, rated and approved for such use in accordance with ASME A112.4.1.


504.7 Required pan.

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 galvanized steel pan having a material thickness of not less than 0.0236 inch (0.6010 mm) (No. 24 gage), or other pans approved for such use.


504.7.1 Pan size and drain.

The pan shall be not less than 11/2 inches (38 mm) in depth and shall be of sufficient size and shape to receive all dripping or condensate from the tank or water heater. The pan shall be drained by an indirect waste pipe having a diameter of not less than 3/4 inch (19 mm). Piping for safety pan drains shall be of those materials listed in Table 605.4.


504.7.2 Pan drain termination.

The pan drain shall extend full size and terminate over a suitably located indirect waste receptor or floor drain or extend to the exterior of the building and terminate not less than 6 inches (152 mm) and not more than 24 inches (610 mm) above the adjacent ground surface. Where a pan drain was not previously installed, a pan drain shall not be required for a replacement water heater installation.

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