Water Leaking from Boiler: Causes and Solutions

Water Leaking from Boiler: Causes and Solutions

A boiler is an essential appliance in many homes, providing hot water and heating. However, sometimes water might start leaking from it, which can be concerning. Understanding why this happens and knowing how to address it can save you from potential damage and costly repairs.

Here’s a simple guide to help you understand the common reasons for boiler leaking water from overflow pipe and what you can do about them.

5 Common Causes of Water Leaking from a Boiler

Here are some common causes of water leaking from a boiler that we should know:

1.    Leaking from the Relief Valve

Reason: The pressure relief valve is designed to release excess pressure from the boiler. If the valve is leaking, it might indicate that the pressure inside the boiler is too high.

Solution: Check the pressure gauge. If the water leaking from the pressure relief valve on boiler is above the recommended level (usually around 1-2 bars), you might need to bleed your radiators to reduce the pressure. If the problem persists, the valve might be faulty and need replacement.

2.    Leaking from Underneath the Boiler

Reason: Leaks from the bottom can be due to corrosion in the pipes or the boiler itself, loose connections, or a faulty seal.

Solution: Inspect the boiler leaking water from pipes and connections for visible damage or rust. Tighten any loose fittings and consider using a sealant for minor leaks. If the boiler or its components are heavily corroded, you might need professional help to replace the affected parts.

3.    Leaking from the Overflow Pipe

Reason: The overflow pipe usually leaks when there is an issue with the boiler’s expansion vessel or if the boiler is overfilled.

Solution: Check the boiler pressure and release some water if it is too high. If the expansion vessel is faulty, it might need to be repaired or replaced by a technician.

4.    Leaking from the Top of the Boiler

Reason: Boiler leaking water from top are often due to issues with the pressure relief valve or the auto air vent.

Solution: Check the pressure relief valve as mentioned earlier. If the auto air vent is leaking, it may need cleaning or replacement.

  1. Leaking from the Outside

Reason:. Water leaking from the boiler outside can be due to condensation, poor installation, or damage to external components.

Solution: Ensure that the boiler and its components are properly insulated and protected from the elements. If you suspect poor installation, it might be worth getting a second opinion from a certified technician.

5.    Water Leaking from Bottom Of Boiler

Reason: Similar to general leaks underneath, this can be due to a variety of issues including corrosion, loose fittings, or a cracked heat exchanger.

Solution: Perform a visual inspection and tighten any loose connections. If you suspect a cracked heat exchanger, call a professional as this is a complex issue.

3 Things to Check Before You Panic

A leaking boiler can be worrying, but it doesn’t always mean you need a costly replacement. Here are three things to check first:

Pressure Issues

Boilers have an outlet pipe to release extra pressure, which can cause occasional drips. Large amounts of water indicate too much pressure.

What to Do: Check the pressure gauge. If it’s in the red zone, call a professional to reduce the pressure.

Loose Joints

Boilers expand and contract with temperature changes, loosening joints.

What to Do: Check all the fittings for leaks. Tighten any loose joints slightly. If unsure, call a professional.

Damage to Seals or Body

Over time, the boiler’s seals can harden or crack.

What to Do: Inspect for cracks or damaged seals. If the boiler is old or newly installed with suspected overpressure, call a professional.

Preventive Measures

  • Regular Maintenance: Schedule regular maintenance checks with a professional to ensure that your boiler is in good working condition.
  • Monitor Boiler Pressure: Keep an eye on the pressure gauge and make adjustments as necessary.
  • Inspect for Corrosion: Regularly inspect the boiler and its pipes for any signs of rust or corrosion.

When to Call a Professional?

While minor leaks can sometimes be fixed by tightening connections or releasing pressure, more serious issues like a cracked heat exchanger, faulty expansion vessel, or persistent high pressure should be handled by a professional. Regular servicing from Temperature Zone Corp can help prevent these problems and ensure your boiler operates safely and efficiently.


A leaking boiler can be a sign of various issues ranging from high pressure to corrosion. By understanding the common causes and knowing when to seek professional help, you can keep your boiler running smoothly and avoid costly repairs.