Requirements for Water Heater TPR Discharge Pipes:

  1. Must not be directly connected to the home drainage system;
  2. Must discharge through an air gap located in the same room as the water heater.;
  3. Must not be smaller than the diameter of the TPR outlet;
  4. Must not serve multiple valves;
  5. Must discharge to the floor, water heater pan, waster receptor or outdoors;
  6. Must terminate no more than 6 inches above the floor or waste receptor;
  7. Must discharge as to not cause personal injury or structural damage;
  8. Point of discharge must be readily observable;
  9. No traps are allowed;
  10. Must flow by gravity;
  11. No threaded connection at the end of the pipe;
  12. No valves or fittings;
  13. Must be constructed of materials referenced in P2904.5* or tested, rated and approved in accordance with ASME A112.4.1



Although what is acceptable can vary by jurisdiction, the following materials are listed in the 2015 International Plumbing Code as being acceptable for TPR discharge pipe:

  • Brass pipe;
  • CPVC;
  • Copper or copper-alloy tubing (Types K, WK, L WL, M, or WM);
  • PEX;
  • High-density PEX (PEX-AL-HDPE);
  • Ductile iron pipe;
  • Galvanized steel pipe;
  • Polyethylene/aluminum/ Polyethylene (PE-AL-PE) composite pipe;
  • Polyethylene of raised temperature  (PE-RT) plastic tubing;
  • Polypropylene plastic pipe or tubing;
  • Stainless steel pipe (types 304 or 304L)
  • Stainless steel pipe (types 316 or 316L)


  • PVC is not acceptable.
  •  If the discharge pipe is a flexible material, some method should be used that will hold the termination in place during discharge.