Why Is My Boiler Leaking Water from Underneath?

There would hardly be a home in the UK without a boiler. A boiler is among the most essential items that a home in the UK must have. It not only provides hot water for showers and taps but is primarily used to heat homes, making a boiler essential, especially during the colder months.

Like other equipment, especially equipment with moving parts and water, boilers are prone to malfunction at any time. It may develop a fault and sometimes may completely stop working. Water leakage from under the boiler is one of the critical situations every home may have experienced. Water leakage may not appear to be a serious issue, but it can lead to a major breakdown later and incur high costs. Therefore, if a boiler is leaking water from underneath, it should not be ignored. It needs immediate fixing. But without understanding the actual cause, any remedial measure may not work as expected.

Keep reading this blog to know everything about leakage of water from underneath a boiler, the actual reasons behind it, and most importantly, what you need to do when it happens. 

Boiler Leaking Water From Underneath – An Overview

Leakage of water from a boiler is not a rare or unexpected situation; it is a normal occurrence. However, just taking it as a routine matter may not be the right and prudent approach. While it indicates an issue with critical boiler components, unaddressed or prolonged leakage can lead to a serious fault and significant repair or replacement costs.

In general, water leaking from underneath the boiler may happen due to one or more reasons, as mentioned below:

1.       Fault or complete failure of an internal component of the boiler, such as a heat exchanger or expansion vessel.

2.       Faulty valves, such as the Pressure Relief Valve (PRV).

3.       Higher water pressure, especially if it goes into the red zone, i.e., 2.5 bars or more.

4.       Corroded or weakened pipework, outlived seals.

5.       Wrong installation of a boiler or unprofessional repair and maintenance work, which may involve loose joints and connections.

So, water may start leaking from underneath a boiler due to any one or multiple reasons as mentioned above. Even if the fault is inside, water ultimately tends to run towards the floor, from underneath the boiler. Therefore, it is important to understand that the actual cause of water leaking from below may not be pipe leakage; it can often originate from internal components.

Why Is My Boiler Leaking Water From Underneath – Most Common Reasons

The actual causes of water leaking from underneath a boiler may vary on a case-by-case basis, but most often it happens due to one of the following faults:

1.     Higher Boiler Pressure And Pressure Relief Valve

Boilers are designed to operate optimally at a water pressure of approximately 1.0 to 1.5 bar. As water is heated, or if more water enters the boiler during repressurization, the boiler pressure may exceed 1.5 bar. Normally, it is not a serious issue, but it enters a danger zone if pressure exceeds 2.5 bars. At this point, the role of the Pressure Relief Valve (PRV) starts. It is a safety device that allows the release of extra pressure from the boiler. When it happens, the extra water is released from the discharge pipe of the PRV, which naturally flows downwards and may appear below the boiler. 

Generally, the boiler experiences higher pressure due to the following reasons:

·         While topping up the water pressure, the system might have been overfilled.

·         It may happen due to the complete failure of the Expansion Vessel.

·         The condensate pipe was blocked for some unknown reason.

·         Radiator bleeding was not performed in a timely manner for an extended period.

The problem of overpressurization of a boiler or PRV failure can be easily identified if any of the following are observed:

1.       If water starts coming from a small pipe located beneath the boiler. This is the pipe that allows drainage of extra water when the PRV is activated.

2.       If boiler pressure has entered the danger zone, i.e., more than 2.5 bars. This can be observed on the pressure gauge. Most of the pressure gauges have an area marked in red. If the needle enters this area, it means the pressure is higher than the required level.

3.       If the PRV is releasing extra water from the system, only when the boiler is hot, it is also an indication that higher water pressure is causing water to leak from below the boiler.

2.     Corroded Internal Parts of the Boiler

Several internal parts of a boiler are made up of metals, such as copper pipes. Heat exchangers and expansion vessels are also included in the metallic internal parts of the boiler. It is quite a routine and natural process that if metals are exposed to water and oxygen, they may corrode over time. When a metallic part is corroded, it becomes weakened, leading to cracks and small holes. If any of these internal metallic parts are corroded, there is a high likelihood of water leaking from them and eventually appearing below the boiler.

Any such incident can be identified from the following:

·         The leaked water appears rusty and discolored.

·         Leakage is in the form of slow seepage, instead of rapid dripping or consistently flowing water.

·         If you notice signs of rust and corrosion at specific points, such as connectors and joints, or even on some of the exterior of some of the components.

Such a situation is quite common with the older boilers. Ideally, the newer boilers should not develop corrosion or rust, but it cannot be completely ruled out, especially when service and maintenance are not being done properly and in a timely manner.

3.     Heat Exchanger Is Faulty

The heat exchanger is meant to transfer heat from the burning of the fuel, mostly gas, to the water inside the boiler. That makes this component highly critical. Over the years, due to consistent use and poor maintenance, this critical component may develop corrosion and cracks. When it happens, water may start leaking, which appears beneath the boiler.

If your boiler's heat exchanger is corroded or cracked, it could be a serious, costly issue, as repairs can be quite high. Although an expert opinion from a qualified, Gas Safe-registered engineer may be needed, it is often better to replace the boiler than repair the heat exchanger.

4.     Fault In Pump Seals

Boilers are fitted with a water pump that pumps hot water around the entire heating system. This pump has seals to prevent water leaks. Over time, these seals tend to wear out, which causes water leakage.

This fault can be identified from the following:

·         If water appears when heating is on.

·         If you notice leaks near the location of the water pump.

·         Unusual noises, such as humming or hissing sounds, are emerging from the pump.

5.     Problems and Faults With Connections and Joints

The boilers have different joints, connections, seals, and washers, which are likely to be damaged and degraded with consistent usage over time. Moreover, the joints and connections may not be properly tightened during installation or repair. In any such eventuality, water leaks may occur, which can be observed from the following:

·         Dripping water around joints and connections.

·         Dampness around the boiler.

·         Frequent small leaks.

6.     Blocked or Frozen Condensate Pipe

A condensate pipe is a plastic pipe fitted with the condensing boilers to drain out slightly acidic water from them. This pipe can be blocked over time due to debris. During severe cold weather, this pipe often freezes and becomes blocked. When this pipe is blocked, the drained water can flow back into the boiler, causing a leak beneath it.

7.     Wrong or Unprofessional Installation

Correct installation is essential to the proper operation of a boiler. That's why it is necessary to get it done by a Gas Safe-registered engineer. However, if for any reason the boiler was not installed correctly, you may experience problems like water leaking from underneath. Moreover, if the repair, service, or maintenance is not done through a qualified Gas Safe-registered engineer, you may also face a water leak.

Important

In most cases, especially when the fault is inside the boiler, never try to fix it on your own. Always call a Gas Safe-registered engineer to determine the cause and resolve the issue.

Conclusion

Boilers are meant to provide hot water and heating. Normally, a boiler meets this requirement, but it may experience issues and faults. Leaking water under the boiler is one such issue that users often ignore or take lightly, but it can escalate into a serious problem with high costs. The primary cause of water leaking from beneath the boiler is typically a fault or failure in its internal components, such as the heat exchanger or expansion vessel.

It may also happen due to loose joints and connections, as well as a blocked condensate pipe. Mostly, this also occurs when the boiler pressure exceeds 2.5 bars, causing water to be released through the pressure relief valve. Whatever the reason, never ignore a leak beneath a boiler, even if it is minor. Identify the leak and the reasons causing it, and call a Gas Safe-registered engineer to fix the problem.