Temperature and Pressure Relief Valve Including Discharge Line Requirements
1. All water heaters shall be provided with an AGA or UL Approved Pressured Relief Valve. The Relief Valve shall be located in a manner that does not obstruct the valve lever.
2. The Pressure Relief Valve shall be installed on the hot water side at the top of the water heater or at the location designated by the manufacturer.
3. The Pressure Relief Valve's sensing element shall be immersed in the top 6 inches of the tank.
4. The Pressure Relief Valve Drain shall be of galvanized steel, copper pipe, or flexible copper tubing. The drain shall run continuously downward from the outlet opening of the Pressure Relief Valve.
5. The Discharge Line must terminate at the outside of the building, at a point not higher than 2 inches or less that 6 inches from ground level. The Discharge Line may drain to a utility, sink, trap or floor drain. Such drains must terminate at the minimum of 1 inch above the rim of the sink, trap or train to prevent back syphonage.
6. The end of the Discharge Line may not be capped or threaded and must point downward to the ground.
Drip Leg Option
Prior to May 4, 1987 Plumbing Codes permitted the trapping of Relief Lines. When replacing a water heater where such a trapped Relief Line was legally installed in the past, it is now necessary to exercise one of three options:
1. Relocate the water heater so that such trapping is not necessary.
2. Re-pipe the existing Relief Line, if possible, to prevent any rise above the Relief Valve.
3. Provide a Drip Leg, as shown in the illustration, when such rise and consequent trapping cannot be avoided. (Requires Supervisor's Approval).
The Drip Leg shall be secured in a manner which prevents movement, and the 3/8 inch opening in the Drip Leg shall be directed away from access to the water heater controls.