The discharge tube on a water heater relief valve must be the correct diameter to safely and effectively handle water or steam released during high-pressure or high-temperature events. A tube that is too narrow restricts flow, potentially creating dangerous pressure buildup or backflow, and may not comply with building codes. This guide explains why proper sizing is important, how to diagnose and fix the issue, and what to do to ensure compliance and safety.

1. Ensures Safe Flow:

• A properly sized tube allows water and steam to exit freely, preventing pressure buildup.

2. Prevents Backflow:

• A narrow tube can cause water to back up into the relief valve, increasing stress on the system.

3. Meets Code Requirements:

• Building codes specify that the discharge tube must match or exceed the diameter of the T&P relief valve outlet (commonly ¾ inch).

4. Protects Property and Occupants:

• Ensures that water or steam is directed safely away without restriction.

1. Pressure Buildup:

• Restricts water or steam release, potentially leading to dangerous pressure levels.

2. Valve Damage:

• Increased back pressure can damage the T&P relief valve, reducing its effectiveness.

3. Non-Compliance:

• A discharge tube that is too narrow violates safety standards and building codes.

4. Increased Liability:

• Improper installation could lead to accidents, making you liable for damages or injuries.

1. Measure the Diameter:

• Check the diameter of the T&P valve outlet, typically ¾ inch, and compare it with the discharge tube.

• If the tube is smaller than the valve outlet, it is too narrow.

2. Inspect for Flow Restrictions:

• Observe the tube for signs of blockage, corrosion, or kinks that may restrict flow.

3. Check Building Code Compliance:

• Local plumbing codes often require discharge tubes to match or exceed the T&P valve outlet diameter.

1. Turn Off the Water Heater:

• Shut off power (electric water heaters) or gas (gas water heaters) to prevent the system from heating while you work.

2. Select the Correct Tube:

• Purchase a discharge tube with a diameter of ¾ inch or larger, made of code-compliant materials such as:

• Copper

• CPVC

• Galvanized steel

3. Remove the Narrow Tube:

• Unscrew the existing discharge tube from the T&P valve using an adjustable wrench.

4. Install the Properly Sized Tube:

• Steps:

1. Wrap the threads of the T&P valve with Teflon tape to ensure a tight seal.

2. Attach the new tube, ensuring it is securely threaded into the valve.

3. Confirm that the tube is sloped downward and terminates no more than 6 inches above the floor or drain.

• Tips:

• Avoid sharp bends or obstructions in the tube.

• Ensure the end of the tube is not threaded to prevent capping.

5. Test the System:

• Open the T&P valve briefly to release water and verify that the flow is unrestricted and directed safely away.

1. Verify Compatibility During Installation:

• Always match the discharge tube diameter to the T&P valve outlet.

2. Inspect Annually:

• Check the tube for signs of wear, corrosion, or narrowing due to mineral buildup.

3. Adhere to Local Building Codes:

• Consult a licensed plumber or building inspector to ensure compliance with applicable codes.

• If you are unsure about selecting or installing the correct discharge tube.

• For assistance with inspecting or upgrading your water heater system.

• To address additional issues with the T&P valve or plumbing system.

• New Discharge Tube: $10–$50, depending on material and length.

• Professional Installation: $100–$300, including labor and materials.

1. Protects Safety:

• Ensures the T&P valve functions as intended, preventing pressure buildup or backflow.

2. Ensures Compliance:

• Avoids code violations and potential fines during inspections.

3. Prevents Equipment Damage:

• Reduces strain on the T&P valve and water heater system.

4. Minimizes Liability:

• Reduces the risk of accidents, property damage, or injuries.

A discharge tube that is too narrow compromises the safety and effectiveness of your water heater’s relief valve. By replacing it with a properly sized, code-compliant tube, you can ensure safe operation and compliance with building standards. For professional assistance, consult a licensed plumber to guarantee proper installation and functionality.