A hot water tank valve, specifically the Temperature and Pressure Relief (TPR) valve, works by automatically opening to release excess pressure or dangerously high temperatures inside the water tank, preventing potential explosions or damage.
Here's a breakdown of how it functions:
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Purpose: The primary function of the TPR valve is to safeguard the water heater from exceeding safe operating limits.
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Activation: The valve activates under two main conditions:
- Excessive Pressure: If the water pressure inside the tank rises above a pre-set limit (typically 150 psi), the valve opens. This pressure increase can be caused by various factors, including the heating of water which causes it to expand.
- Excessive Temperature: If the water temperature inside the tank exceeds a pre-set limit (usually 210 degrees Fahrenheit), the valve opens. This high temperature can be a result of a malfunctioning thermostat.
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Operation: When either the pressure or temperature limit is reached, the valve opens mechanically. This allows hot water to escape from the tank through a discharge pipe.
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Pressure Relief: By releasing water, the TPR valve reduces the internal pressure within the tank.
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Temperature Relief: Releasing hot water also lowers the overall temperature inside the tank.
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Automatic Reset: Ideally, once the pressure or temperature returns to a safe level, the valve should automatically close. However, a valve that has been triggered may sometimes leak afterward, indicating a potential problem with the valve itself or the water heater system.
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Safety Measure: The TPR valve is a crucial safety device, and it is essential to ensure it is functioning correctly. Regular inspection and maintenance are recommended. Never cap or block the discharge pipe, as this defeats the purpose of the valve and can create a hazardous situation.
In summary, the TPR valve acts as a pressure and temperature "escape route" for a water heater. When either parameter exceeds safe limits, the valve opens to release hot water, reducing the risk of a tank rupture or explosion.
