How to Replace a Water Heater Relief Valve: DIY Installation Tips

If your water heater relief valve is leaking or not functioning properly, you’ll want to know how to replace a water heater relief valve. This important valve helps keep your water heater safe by regulating temperature and pressure.

Over time, it can wear out or become faulty. Replacing it is a straightforward job, and in this guide, we’ll walk you through the process step by step to get your water heater running safely and smoothly again.

Water Heater Relief Valves: What They Are and How They Work

A water heater’s temperature and pressure relief valve (TPR or T&P relief valve) is a vital safety feature designed to control temperature and pressure levels in tank-type water heaters. It’s important to note that tankless water heaters also require a pressure relief valve, as mandated by ANSI and CSA standards.

How the TPR Valve Works

When you need hot water, the electric heating elements or gas burner (depending on the type of water heater) activate to heat the water stored in the tank. Once the water reaches the set temperature, the thermostat and control valve automatically shut off the system.

However, if either the thermostat or control valve fails, the temperature and pressure can quickly rise to dangerous levels. This is where the TPR valve comes in.

The TPR valve is designed to open and release water when the temperature or pressure inside the tank exceeds safe limits. This helps prevent excessive pressure and overheating, which could otherwise lead to dangerous conditions.

Preventing Dangerous Pressure and Temperature Buildup

When the water temperature exceeds 212°F, it reaches the boiling point, turning into steam. The steam rapidly expands, releasing enough energy to cause an explosion. Without a functioning TPR valve, this pressure can weaken the tank and potentially lead to a rupture or explosion.

The TPR valve includes a probe that is immersed in the first six inches of water inside the tank. This probe measures the water temperature, which is typically set to a safe maximum of 210°F. If the probe detects an excessive temperature—often due to a thermostat failure—the relief valve opens to release hot water until the temperature drops below the reset value.

Pressure Relief

In addition to temperature control, the TPR valve also manages pressure. The maximum working pressure for most water heaters is typically 150 psi, which is listed on the unit’s data plate. The relief valve should never exceed this pressure rating. When the pressure inside the tank reaches this limit, the valve opens to release excess pressure, preventing damage to the tank and other components.

With this system in place, the TPR valve ensures the safety of your water heater by preventing dangerous temperature and pressure buildup, keeping your home safe from potential hazards.

Is Leaking from a Water Heater Relief Valve Normal?

If your water heater’s relief valve is leaking or dripping, there are typically two possible causes:

• Excessive Pressure and Temperature: When the water temperature or pressure becomes too high, the relief valve opens to release the excess. As water heats up, it expands, and in a closed system, there’s nowhere for the expanding water to go except through the TPR valve. This results in dripping or discharge.
• Faulty Relief Valve: If the valve is broken or not sealing properly, it may remain open. Sediment buildup or wear can prevent the valve from closing completely, causing it to drip continuously.

In plumbing terms, dripping is referred to as “dribbling” or “weeping,” which occurs when the valve releases small amounts of water during operation.

While small leaks might seem insignificant, they can waste water and energy. In more severe cases, they can lead to property damage or indicate a larger system issue.

Preventing Damage from a Leaking Relief Valve

To minimize the risk of damage, it’s essential to install a discharge pipe. One end of the pipe should be securely connected to the TPR valve, while the other end should terminate a few inches above the floor drain or drain pan. This ensures any discharged water flows safely away from the unit.

Some experts recommend not terminating the discharge pipe into a home drain or outside, as it’s important to monitor the discharge. Keeping the end visible allows you to detect when the valve is releasing water, giving you time to address the issue.

How to Prevent Pressure-Related Leaks

To reduce the risk of the TPR valve opening due to increased temperature or pressure, installing an expansion tank is highly recommended, especially for closed systems. The expansion tank helps manage water pressure and reduces the chances of triggering the relief valve.

How to Test a Temperature and Pressure Relief Valve (TPR)

Testing your water heater’s temperature and pressure relief valve is crucial for maintaining safety and ensuring proper function. This valve helps prevent the tank from overpressurizing or overheating by releasing water when necessary. Here’s how to test it:

1. Locate the TPR Valve. The TPR valve is typically found on the side or top of the water heater tank. It has a lever or pull-tab that you can manually lift to test its function.
2. Lift the Lever. Carefully lift the lever on the TPR valve to check its operation. Water should flow through the discharge pipe when the lever is lifted. This ensures the valve is working properly by allowing pressure to escape.
3. Check the Water Flow. Be cautious—when you lift the lever, hot water may flow through the discharge pipe. Make sure no one is near the outlet, as the water could be scalding.
4. Allow the Valve to Reset. Once you release the lever, the valve should reset and stop releasing water. If the valve doesn’t stop releasing water or fails to reset completely, it may need to be replaced.
5. Inspect for Leaks. Check the area around the valve and the discharge pipe for any signs of leaking water. Leaks can indicate a problem with the valve, such as wear or a faulty seal.
6. Replace if Necessary. If the TPR valve fails the test, or if it continues to leak after resetting, turn off the water and power supply to the heater. Replace the valve with a new one to restore safe operation.

Final Tip: Test the TPR valve at least once a year to ensure your water heater remains safe and functional. A properly working valve is essential to prevent overheating or excessive pressure buildup in the tank.

How to Replace a Water Heater Relief Valve – Installation Tips

Here’s a detailed, step-by-step guide on how to replace a temperature and pressure relief (TPR) valve on a water heater:

Preparation

Before beginning, make sure you have all the tools and materials you’ll need:

• Garden hose
• Pipe sealer or Teflon tape (to prevent leaks)
• Replacement T&P valve
• Adjustable wrench or pipe wrench (in case you need extra leverage)
• Bucket (optional, for draining)

Instructions

Step 1: Turn Off Power and Water Supply

Start by turning off all power sources and water supply to your water heater to ensure safety.

• For electric water heaters, locate the breaker panel and switch off the power to the water heater to avoid electrical hazards.
• For gas water heaters, shut off the gas supply by turning the gas valve to the “off” position.
• Shut off the water supply: Close the cold water shut-off valve that feeds into the water heater to prevent additional water from entering the tank.

Step 2: Prepare for Draining

In order to replace the T&P valve, you will need to drain the water heater. This step ensures that no water remains in the tank while you’re working on the valve.

• Attach the garden hose: Connect one end of a garden hose to the drain valve located at the bottom of the water heater.
• Route the hose: Direct the other end of the garden hose to a suitable drainage area, like an outdoor drain or a floor drain, ensuring that hot water can safely drain away.

Step 3: Release Pressure

Before draining, it’s essential to relieve pressure inside the tank to avoid injury or damage.

• Open the TPR valve: The T&P valve is typically located near the top or side of the water heater, often marked with a lever or a pull-tab. Open this valve to allow air to enter the tank, which will make draining easier.
• Open the drain spigot: Once the valve is open, open the drain valve to begin releasing water. Caution: The water might be hot, so wear gloves or use a long hose to keep a safe distance from the water stream.

Step 4: Drain the Water Heater

• Allow the tank to fully drain, ensuring no more water is flowing out. Depending on the size of your tank, this might take some time.
• Close the drain spigot: After the water stops flowing, close the drain valve to halt the draining process.

Step 5: Remove the Old T&P Valve

• Using a wrench or pipe wrench, carefully unscrew and remove the old T&P valve from its mounting spot. Be sure not to damage the threads of the valve connection, as this could make installing the new valve difficult.
• Inspect the old valve for signs of corrosion or damage, which could be an indicator of why it failed in the first place.

Step 6: Prepare the New T&P Valve

• Take the replacement T&P valve and apply pipe sealer or Teflon tape to the threaded portion of the valve. This ensures a leak-free seal when you install the new valve. If you use Teflon tape, wrap it around the threads in the direction of the thread rotation (usually clockwise).
• Position the valve: Make sure the valve is in the open position before installation to allow water to flow freely when the system is filled.

Step 7: Install the New T&P Valve

• Screw the new T&P valve into the opening where the old valve was removed.
• Tighten it by hand first, ensuring that it’s properly aligned with the threads.
• Once aligned, use the wrench or pipe wrench to securely tighten the valve, but avoid over-tightening as this can damage the valve or the threads.

Step 8: Refill the Tank

• Turn on the cold water supply valve: Open the cold water shut-off valve to begin filling the tank with water.
• Open a hot water tap: Open a hot water faucet somewhere in your home (e.g., a bathroom sink or bathtub) to allow air to escape from the tank as it fills.
• Once water begins to flow steadily from the faucet, this indicates that the air has been purged from the system and the tank is filling properly.

Step 9: Close the T&P Valve

• Once the water begins flowing in a steady stream, close the T&P valve. This will ensure the system is pressurized and water can be safely heated.

Step 10: Restore Power and Test the Heater

• Turn the power back on: Once the tank is full of water, turn the power supply back on for the electric water heater or relight the pilot light for the gas heater.
• Test the new T&P valve: Once the heater is operating, test the new T&P valve by manually lifting the lever to make sure it opens properly and that water is released.
• Check for leaks: Look around the area where the valve is installed and check for any signs of leaking. If there are any, you may need to tighten the valve a little more or reapply pipe sealant.

Additional Tips:

• Ensure the tank is full before turning on the heater. Running the heater with an empty tank could damage the heating elements or cause the tank to overheat.
• Test the T&P valve regularly, as it is a critical safety feature designed to prevent excessive pressure or temperature buildup inside the tank.
• Replace T&P valves as needed: If the old valve is showing signs of wear, corrosion, or malfunction, it’s important to replace it immediately to avoid potential leaks or damage to the water heater.

Why It’s Crucial to Ensure Your TPR Valve Is Properly Sized: The Risk of Explosion Is Real

A TPR valve is both pressure- and temperature-sensitive, providing essential protection for your water heater by preventing dangerous pressure and temperature buildups, including the risk of rupture or explosion.

If the water inside the tank reaches its boiling point of 212°F, it turns into steam, rapidly expanding in volume and releasing a significant amount of energy. This sudden pressure spike makes the water heater and its surroundings unsafe, potentially leading to catastrophic failure.

When the TPR valve is correctly installed and functioning, it will discharge the overheated water once the pressure or temperature exceeds safe limits. Simultaneously, cold incoming water enters the tank to help reduce both pressure and temperature, restoring safety.

However, if the BTU capacity of the TPR valve is too low compared to the heater’s BTU output, the valve won’t be able to relieve the pressure effectively. This mismatch increases the risk of the tank rupturing or even exploding.

How to Check the Proper Sizing of Your TPR Valve

To ensure the TPR valve is sized correctly for your water heater, check the capacity listed on the valve’s data plate. It’s important that the valve’s BTU capacity meets or exceeds the BTU input of the water heater.

• For gas water heaters, the BTU rating indicates the heating power.
• For electric water heaters, the power is listed in kilowatts (kW). To convert kW to BTU/hr, use this formula:
  1 watt = 3.413 BTU/hr.

For example, if the heating elements have a power of 5500 watts, you can calculate:
5500 watts × 3.413 = 18,771 BTU/hr.

Ensuring the proper sizing of the TPR valve is crucial for safe operation and to prevent the risk of a dangerous incident.