A Water Heater Pressure Relief Valve is a critical safety device installed on residential water heaters. Its main function is to prevent excessive pressure or temperature buildup inside the water heater tank. Without it, your water heater could become a serious safety hazard.

In this guide, we’ll explain what a pressure relief valve is, how it works, why it's essential, how to test it, and when to replace it—helping you maintain a safe and efficient water heating system.

What Does a Water Heater Pressure Relief Valve Do?

The Water Heater Pressure Relief Valve (also known as a TPR valve or T&P valve) is a spring-loaded safety mechanism. It is typically located on the side or top of the tank and connected to a discharge pipe that directs hot water away safely if the valve is triggered.

If temperature or pressure inside the tank rises beyond safe limits, this valve opens automatically to release water or steam, reducing pressure and preventing the risk of a tank explosion or rupture.

How the Water Heater Pressure Relief Valve Works

The valve activates under two main conditions:

  • High Pressure: If internal pressure exceeds 150 PSI (pounds per square inch).

  • High Temperature: If water temperature exceeds 210°F (99°C).

Here’s how it functions:

  1. Detection: The valve senses unsafe pressure or temperature levels.

  2. Release: It opens automatically to let out hot water or steam through the discharge pipe.

  3. Reset: Once conditions stabilize, the valve closes again, allowing normal operation to continue.

This simple yet vital mechanism keeps your water heater running safely and efficiently.

Why Is the Water Heater Pressure Relief Valve Important?

The Water Heater Pressure Relief Valve is essential to the safe operation of your water heater. Here’s why:

1. Prevents Explosions

If pressure builds up without release, the tank can explode. This valve ensures dangerous pressure is released safely.

2. Stops Overheating

If the thermostat malfunctions, water can become dangerously hot. The valve prevents scalding by releasing overheated water.

3. Extends the Life of Your Water Heater

By minimizing stress on the tank, the valve helps reduce wear and extends the system’s lifespan.

4. Ensures Code Compliance

Local building codes and national safety standards require a working pressure relief valve on all water heaters.

How to Test Your Water Heater Pressure Relief Valve

Testing your Water Heater Pressure Relief Valve is easy and should be done at least once a year. Here’s how:

Step 1: Locate the Valve

Look for the valve on the top or side of your water heater tank. It has a small lever attached.

Step 2: Place a Bucket Below

Position a bucket under the discharge pipe to catch any released water.

Step 3: Lift the Lever

Gently lift the lever to let a small amount of water and steam escape. A hissing sound indicates it’s working.

Step 4: Let the Valve Close

Release the lever. The valve should shut off completely. If it continues to drip, it may need replacement.

Step 5: Inspect for Damage

Check for rust, corrosion, or mineral buildup around the valve and pipe.

When to Replace a Water Heater Pressure Relief Valve

Over time, the Water Heater Pressure Relief Valve can wear out or become clogged. You should replace it if:

  • It leaks continuously after testing.

  • There’s visible corrosion or mineral deposits.

  • Nothing happens when you lift the lever.

  • It’s over 5 years old and hasn’t been inspected.

Timely replacement is an inexpensive way to avoid dangerous pressure buildup and costly repairs.

How to Replace a Water Heater Pressure Relief Valve

If you need to replace your Water Heater Pressure Relief Valve, follow these steps carefully—or consult a licensed plumber:

Step 1: Turn Off Power and Water

Shut off electricity or gas to the heater. Close the cold water supply valve.

Step 2: Drain the Tank Slightly

Open a hot water tap and drain a few gallons of water using the drain valve.

Step 3: Remove the Old Valve

Use a wrench to carefully unscrew the old valve. Watch for hot water in the line.

Step 4: Install the New Valve

Wrap Teflon tape around the new valve’s threads and screw it into place.

Step 5: Restore Power and Water

Turn the water supply back on, let the tank refill, and restore power. Test the new valve to ensure it operates properly.

Final Thoughts

The Water Heater Pressure Relief Valve is a small but vital safety feature that protects your home from high-pressure hazards. Regular inspection, testing, and maintenance are essential for safe and efficient water heater operation.

If you’re experiencing issues or need help replacing a faulty valve, don’t hesitate to contact the professionals at GNV Heating and Air Conditioning. Our team is ready to provide expert service and ensure your water heater is running safely.