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Why Is My Hot Water Tank Overflow Dripping?

Why Is My Hot Water Tank Overflow Dripping?

Have you noticed water dripping from your hot water tank’s overflow pipe?

This is a common issue that many homeowners face, and it can be quite concerning.

The overflow pipe is an essential component of your hot water system, designed to release excess pressure and prevent potential damage or even explosions.

Understanding why your hot water tank’s overflow is dripping is crucial for maintaining the efficiency and safety of your system. As Calgary’s Hot Water Tank Specialists, we investigate the causes and provide actionable solutions.

What is a Hot Water Tank Overflow Pipe?

The overflow pipe, also known as the Temperature and Pressure Relief (T&P) valve, is a critical safety feature in your hot water tank.

Its primary function is to release water when the tank’s pressure or temperature exceeds safe limits.

Diagram showing hot water tank overflow pipe

This prevents the tank from bursting due to excessive internal pressure. The overflow pipe is typically connected to the T&P valve, which is set to open at a specific pressure or temperature threshold.

When either of these limits is reached, the valve opens, allowing water to escape through the overflow pipe and reduce the pressure within the tank.

Common Causes of Hot Water Tank Overflow Dripping

Faulty Temperature and Pressure Relief (T&P) Valve

One of the most common causes of a dripping overflow pipe is a faulty T&P valve. Over time, these valves can wear out and fail to seal properly, leading to continuous drips.

Mineral deposits and corrosion can also build up on the valve, further compromising its ability to function correctly.

Regular maintenance and periodic replacement of the T&P valve can help prevent these issues.

Excessive Pressure in the Water Heater Tank

Excessive pressure within the tank can cause the overflow pipe to drip.

This can result from high inbound water pressure or a malfunctioning pressure regulator.

Water systems that feed into the heater with pressures above the recommended levels can strain the T&P valve, causing it to release water to alleviate the excess pressure. Installing a pressure regulator can help control the incoming water pressure and protect your system.

Thermostat Issues

Another common cause is incorrect thermostat settings. If the thermostat is set too high, the water heater will produce excessively hot water, increasing the internal pressure.

This can trigger the T&P valve to open and release water. A faulty thermostat that doesn’t regulate the temperature properly can also lead to overheating and excess pressure.

By understanding these common causes, you can begin troubleshooting the issue and take the necessary steps to resolve it. Proper maintenance and timely repairs are essential for ensuring the longevity and safety of your hot water system.

Diagnosing the Problem

To effectively address a dripping overflow pipe, it’s essential to accurately diagnose the underlying issue.

Here are some steps to help you pinpoint the cause:

  1. Inspect the T&P Valve:
    • Check if the T&P valve is functioning correctly. Lift the valve’s test lever and release it. If it doesn’t snap back into place or continues to drip, it may need replacement.
    • Look for signs of corrosion or mineral buildup around the valve, which can prevent it from sealing properly.
  2. Check for Tank Corrosion:
    • Examine the tank for signs of rust or corrosion, particularly around the base and seams. Corrosion can weaken the tank and lead to leaks.
    • Regular maintenance, such as flushing the tank to remove sediment, can help prevent corrosion.
  3. Inspect Pipe Fittings and Connections:
    • Over time, pipe fittings can loosen or deteriorate, causing leaks. Tighten any loose fittings and replace any that are damaged.
    • Ensure that the drain valve at the bottom of the tank is tightly closed and not leaking.

How to Fix a Dripping Overflow Pipe

Once you’ve diagnosed the issue, you can take the appropriate steps to fix it.

Here are some common solutions:

Replacing the T&P Valve:

  1. Turn Off the Power and Water Supply:
    • Shut off the electricity or gas supply to the water heater.
    • Close the cold water inlet valve to prevent more water from entering the tank.
  2. Drain the Tank:
    • Connect a hose to the drain valve and direct the water to a suitable drainage location.
    • Open the drain valve and allow some water to flow out, reducing the tank’s internal pressure.
  3. Replace the T&P Valve:
    • Unscrew the old T&P valve using a wrench.
    • Wrap the threads of the new valve with Teflon tape and screw it into place.
    • Restore the water and power supply and check for leaks.

Installing a Pressure Regulator:

  1. Shut Off the Main Water Supply:
    • Locate the main water supply valve and turn it off.
  2. Install the Pressure Regulator:
    • Cut the main water line using a pipe cutter.
    • Install the pressure regulator according to the manufacturer’s instructions.
    • Restore the water supply and adjust the regulator to the recommended pressure (usually around 80 PSI).

Adjusting or Replacing the Thermostat:

  1. Check the Thermostat Settings:
    • Ensure the thermostat is set to the recommended temperature (typically 120°F).
    • Adjust the thermostat if it is set too high.
  2. Replace the Thermostat:
    • If the thermostat is malfunctioning, turn off the power to the water heater.
    • Remove the access panel and insulation to reach the thermostat.
    • Disconnect the wiring and replace the thermostat with a new one.

Flushing Sediment from the Tank:

  1. Turn Off the Power and Water Supply:
    • Shut off the electricity or gas supply and close the cold water inlet valve.
  2. Drain the Tank:
    • Connect a hose to the drain valve and direct the water to a drainage location.
    • Open the drain valve and allow the water to flow out, removing sediment from the bottom of the tank.
  3. Refill the Tank:
    • Close the drain valve and reopen the cold water inlet valve.
    • Turn on the power or gas supply and allow the tank to refill.

Preventative Maintenance Tips

Regular maintenance is key to preventing future hot water tank overflow pipe issues. Here are some tips:

  • Annual Hot Water Tank Inspections: Check the T&P valve, tank, and pipe fittings at least once a year.
  • Regular Flushing: Flush the tank annually to remove sediment buildup.
  • Temperature Settings: Keep the thermostat set to the recommended temperature (120°F) to avoid excessive pressure.
  • Ventilation: Ensure the area around the water heater is well-ventilated to prevent overheating.

How often should I replace my T&P valve?

  • It is recommended to replace the T&P valve every 3-5 years or if it shows signs of wear or corrosion.


Addressing a dripping overflow pipe promptly is crucial for maintaining the safety and efficiency of your hot water system.

By understanding the common causes and solutions, you can take proactive steps to resolve the issue and prevent future problems.

Regular maintenance and inspections are key to ensuring your hot water tank operates smoothly and safely. If you encounter any difficulties or are unsure about performing these tasks, it is always best to consult a professional plumber.

George Pinel
George Pinel

Master Plumber

I have been involved in this family owned business for 33 years now.

It has always been and will continue to be the core focus of Instant Plumbing & Heating to provide a long lasting relationship with our customers based on trust and integrity of our service and products.

This achieved by using the best quality materials. I as a business owner continue to mentor and treat my staff with the highest regard and respect, this interns helps them deliver to the client great quality workmanship and service.

It is our professional goal to leave a situation better than when we arrived both in how we do our work and in how you feel for having chosen us to do your work, we are in the anxiety reduction business using plumbing and heating service work to do it.

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