During a routine inspection of a commercial building, you notice that a newly installed potable hot water storage tank lacks a temperature and pressure relief (TPR) valve. The building owner claims it's unnecessary because the tank has a separate high-limit temperature control. What Canadian standard or code requires the installation of a TPR valve?

Question: During a routine inspection of a commercial building, you notice that a newly installed potable hot water storage tank lacks a temperature and pressure relief (TPR) valve. The building owner claims it's unnecessary because the tank has a separate high-limit temperature control. What Canadian standard or code requires the installation of a TPR valve?

Answer options:

• CSA B149.1 (Natural Gas and Propane Installation Code)
• CSA B51 (Boiler, Pressure Vessel, and Pressure Piping Code) ✅ National Plumbing Code of Canada (NPC)
• CSA Z21.10.1 (Gas Water Heaters - Storage Water Heaters)

Correct answer: National Plumbing Code of Canada (NPC)

Explanation: The National Plumbing Code of Canada (NPC) mandates the installation of a temperature and pressure relief valve (TPR valve) on hot water storage tanks to prevent over-pressurization and over-temperature conditions. While other codes might relate to gas appliances or pressure vessels, the NPC specifically addresses the plumbing requirements for domestic hot water systems. A high-limit control is a safety feature but does not replace the TPR valve's function as a mechanical relief device.