Temperature and pressure relief valve

Slovak term: Slovenský termín

1. A device that controls both temperature and pressure, releasing water to atmosphere at predetermined settings (WHO 2006).
2. Temperature and pressure relief valve is an automatic safety control valve fitted to a pressurised unvented hot water heater system to protect it from over temperature and/or over pressure failure (Councils of Standards Australia and New Zealand 2003).

Explanation

Temperature and pressure relief valve ensures that the temperature of the water in a pressurised unvented water heater cannot exceed 99°C. Over heating will take place if the normal heater thermostat controls fail. These valves guard against both over-temperature and over-pressure hazards wherever water is stored in unvented containers. They can also incorporate a vacuum breaking (air-inlet) device to protect the cylinder against implosion during the contraction cycle in lower working pressure hot water cylinders. The pressure relief setting should be not more than 20% greater than the input water supply pressure. The pressure relief setting should rated at the same working pressure of the heat (American Society of Sanitary Engineering 2007).

Example

Temperature and pressure relief valve will discharge at predetermined temperature and/or pressures when the temperature of the water in a pressurised unvented water heater exceeds 99°C, or the pre-set pressure exceeds its set pressure level. The valve will discharge to ensure the unvented cylinder remains in a safe state (World Plumbing Council Working Group 2008).

References

• American Society of Sanitary Engineering (2007) Plumbing Dictionary, Sixth Edition
• Councils of Standards Australia and New Zealand (2003). Plumbing and Drainage. Part 0. Glossary of terms. Australian /New Zealand Standards
• WHO (2006) Health aspects of plumbing

Links

• WHO — The Health and Environment Lexicon