Why is My Gas Furnace Relief Valve Leaking After Replacement?
If your gas furnace relief valve is leaking after replacement, there could be several potential reasons. Improper installation, compatibility issues, and problems with other components in the system can all contribute to a leaking relief valve.
Potential Installation Errors
- Incorrect Installation: Ensure that the new relief valve is installed correctly, following the manufacturer’s instructions. Incorrect installation can lead to improper seating or alignment, causing leaks.
- Compatibility Issues: Verify that the new relief valve is compatible with your gas furnace. Using a valve with the wrong pressure rating or design can lead to malfunctioning.
Compatibility Issues
- Pressure Rating: The new valve must be rated for the same pressure as the original. If the new valve has a different pressure rating, it may not function correctly, leading to leaks.
- Thread Size and Type: Ensure the threads on the new valve match those on your furnace. Mismatched threads can prevent a secure seal.
What Causes a Leaking Gas Furnace Relief Valve?
There are several common reasons why a gas furnace relief valve may start leaking, even if it’s not a new replacement.
Excessive Pressure
- High System Pressure: If the system pressure exceeds the relief valve’s set point (usually 30 psi), the valve will open to release excess pressure. This can be due to an overfeeding system, a faulty pressure-reducing valve, or an undersized expansion tank.
- Auto Feeder Issues: An auto feeder that is passing too much water can increase system pressure, causing the relief valve to leak.
Temperature Fluctuations
- Boiler Temperature: If the boiler temperature is too high, it can increase system pressure. Ensure the boiler temperature is within the recommended range.
- Heat Exchanger Leaks: A leaking heat exchanger can allow higher city water pressure to enter the space heating side, increasing system pressure.
Faulty Components
- Expansion Tank Issues: An expansion tank that is not functioning correctly (e.g., no air in the tank or a flooded tank) can cause system pressure to rise, leading to relief valve leaks.
- Faulty Pressure-Reducing Valve: A malfunctioning pressure-reducing valve can allow higher street pressure to enter the system, causing the relief valve to leak.
How Do I Troubleshoot a Leaking Gas Furnace Relief Valve?
To troubleshoot a leaking gas furnace relief valve, you’ll need to gather some tools and follow a step-by-step process.
Tools and Measurements Needed
- Pressure Gauge: To measure system pressure.
- Tire Pressure Gauge: To check the air pressure in the expansion tank.
- Stethoscope: To detect leaks in the pressure-reducing valve.
- Valves and Fittings: To isolate sections of the system for testing.
Step-by-Step Troubleshooting
- Check System Pressure:
- Use a pressure gauge to ensure the system pressure is within the recommended range (usually 12-25 psi). If the pressure is too high, the relief valve will leak.
- Inspect the Expansion Tank:
- Check the air pressure in the expansion tank using a tire pressure gauge. The pressure should match the system pressure when the system is cold.
- If the tank is flooded, it will need to be replaced.
- Test the Pressure-Reducing Valve:
- Use a stethoscope to detect any leaks in the pressure-reducing valve. If water is leaking through the valve, it will need to be replaced.
- Shut off the valves on the feed water pipe and check if the pressure still rises. If it does, suspect the piping to the compression tank is restricted or the tank is flooded.
- Check for Leaks in Other Components:
- Inspect the heat exchanger for leaks. Shut the valves from the domestic water side and see if the pressure still rises.
- Check the auto feeder to ensure it is not passing too much water.
Safety Precautions
- Turn Off Power and Water Supply: Before starting any repairs, ensure the power and water supply to the furnace are turned off.
- Bleed the System: Bleed the radiators to release any air in the system, which can affect pressure readings.
How Do I Fix a Leaking Gas Furnace Relief Valve?
If you’ve identified the cause of the leaking relief valve, you can proceed with the necessary repairs. Here are the steps to fix a leaking gas furnace relief valve.
Materials and Tools Required
- New Relief Valve: Compatible with your gas furnace.
- Expansion Tank: If the existing one is faulty.
- Pressure-Reducing Valve: If the existing one is malfunctioning.
- Tire Pressure Gauge: To check air pressure in the expansion tank.
- Stethoscope: To detect leaks in the pressure-reducing valve.
- Valves and Fittings: For isolating sections of the system.
- Pipe Wrench and Adjustable Wrench: For removing and installing components.
Estimated Costs and Timeline
- Parts Costs:
- New relief valve: $50-$200
- Expansion tank: $50-$200
- Pressure-reducing valve: $50-$200
- Labor Costs:
- If hiring a professional: $100-$500 depending on the complexity and location.
- Timeline:
- DIY: 2-4 hours depending on the complexity of the issue.
- Professional: 1-2 hours for a straightforward replacement, longer if additional issues are found.
Instructions
- Replace the Relief Valve:
- Turn off the power and water supply to the furnace.
- Drain the system to a safe level.
- Remove the old relief valve and install the new one, ensuring it is securely seated and aligned.
- Check and Replace the Expansion Tank:
- If the expansion tank is flooded or not holding air, replace it with a new one.
- Ensure the new tank is precharged to the correct pressure.
- Check and Replace the Pressure-Reducing Valve:
- If the pressure-reducing valve is leaking, replace it with a new one.
- Adjust the valve to ensure it is set to the correct pressure.
- Bleed the System:
- Bleed the radiators to remove any air in the system.
- Test the System:
- Turn on the power and water supply.
- Monitor the system pressure and relief valve to ensure the leak is resolved.
Reference:
- Why does my boilers pressure relief valve keep leaking? – Heating Help
- What could be causing pressure relief valve to release water when boiler pressure is below 30psi? – Reddit
- Why is the relief valve leaking? – Plumbing & Mechanical
