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Here Are Our Most Common Boiler Problems Help and Advice

Boiler leaks

A boiler leak is one of the most common problems with boilers. A boiler leak can cause serious damage to your home and cause electrical malfunctions around the boiler.

There are many reasons why a leaking boiler could happen:

  • Boiler pressure too high
  • Pipes or tanks that are damaged
  • Faulty Component
  • Seals leaks

Leakage should be treated as a serious problem. You should immediately call a heating engineer to inspect a potential leak. Don’t attempt the removal of the boiler casing by yourself to locate the source.

Heating but hot water

Common boiler problems are when hot water is not heated but there is no central heating. There are many reasons this can occur.

First, a combi boiler might be accidentally set to heat only water and not central heating. If the boiler is left on this setting during summer, when radiators are not needed to be heated, but it is not forgotten about, this can happen. The boiler may be set to turn on unexpectedly. To confirm, check the boiler display.

The boiler may be working but the radiators are not heating up. To remove trapped air, blow the radiators.

Your central heating system may not be turning on despite hot water. An engineer registered with Gas Safe will be able investigate the problem and determine the root cause.

Low boiler pressure

Low boiler pressure can cause cold radiators or a shortage of hot water. Low boiler pressure is easily identified on the boiler display panel. A digital dial or a physical dial will indicate the pressure in the system. With slight variations depending on boiler model and manufacturer, the most common pressure level should be 1.5 bars.

Two main reasons a boiler can lose its pressure are:

  • Leakage in the system can cause water to be insufficient in the system, causing pressure to drop.
  • System pressure can be reduced by a leaking radiator.

Re Pressurizing the boiler can fix low boiler pressure. To allow water to re-enter, you will need to open the boiler filling loop. For a complete list of steps, see our boiler guide.

Boiler kettling

The kettling problem is another common problem in boilers. Boiler kettling is caused by too rapid heating of water to reach boiling point. This causes steam to be produced and air to get trapped. The trapped air makes a whistling sound similar to a kettle.

Limescale buildup can cause boiler kettling. This slows down the flow and heats up the boiler too much. An appliance component that is defective could cause water to heat up at higher temperatures than it should.

An engineer can inspect the boiler and determine the source of the kettling. The severity of the problem will determine the solution. Sometimes, the noise-producing component can be removed using other methods like bleeding the radiator. In extreme cases, replacement may be necessary.

Frozen condensate pipe

Many people have to deal with frozen condensate pipes during winter. Each condensing boiler includes a pipe to transport the waste water from the condensing process. The condensate pipe may freeze if temperatures fall below freezing. This will cause the system to be shut down as a precautionary measure.

Warm water is the best method to fix condensate pipes that have frozen. The boiler will then be able to turn itself back on by allowing the waste water to escape the pipe. This guide will explain how to safely remove a frozen condensate tube.

Boiler does not respond to thermostat

To increase efficiency in their homes, there are many thermostats homeowners can choose from. Although these thermostats are great for heating your home, it can be frustrating when they stop responding to your thermostat.

First, check that your thermostat temperature is at least 25 degrees above the room temperature. The thermostat should be working fine if it isn’t.

If the temperature in your room is lower than the thermostat’s temperature, you can either replace the thermostat’s batteries or move it closer to the receiver. If that fails, the thermostat may need to be replaced.

No hot or warm water

There is a problem with your boiler if you have no heat or hot water. There are many reasons why a boiler might stop producing hot water or central heating.

  • The boiler is disconnected from the water, gas, or power supply. These connections can be turned off by accident or during an outage.
  • The boiler pressure can become too high or low, and the system will shut off. This causes a shortage of heat and hot water.
  • A boiler can be stopped from working if it has piping issues such as frozen condensate pipe or airlock.
  • Other faults could be detected by the safety features.

You can have hot water and central heating problems. It is best to contact a Gas Safe registered engineer to check the boiler and fix the problem.

Boiler continues to switch off

Unserviced boilers can eventually start to turn off randomly if they are not taken care of. This could be due to a variety of reasons, including:

  • The system traps air
  • Low boiler pressure
  • Boiler pressure too high
  • Faulty thermostat
  • Pipes clogging with debris and sludge

One of these faults could be the reason your boiler switches on and off constantly. A qualified engineer can determine if the problem can be fixed or if a new boiler is necessary, depending on its severity.

Strange boiler noises

A boiler can make many unusual noises beyond boiler kettling

  • You may hear gurgling sounds – this indicates that there is trapped air in your system.
  • A faulty pump is often responsible for drone noises.
  • If water is delivered from the mains at a high pressure, it will make humming sounds.
  • You may hear a whooshing sound if debris is caught in the air intake pipe, or if the filters are blocked.

Normal boiler noises are not indicative of a danger to the system. However, it is important to call an engineer as soon as possible in order to inspect.

Pilot light turning off

A pilot light may be required to constantly light your larger boiler burner if you have an older boiler. The thermocouple, which is responsible for lighting the pilot switch, can wear down over time.

Do not attempt to fix/replace your pilot light if it keeps on turning off. If you’re not registered with Gas Safe Register, this would mean that the boiler casing must be removed. First, make sure that all your gas appliances work properly. The problem might lie with the gas supply.

If all other gas appliances work properly, it is possible that there is a problem. To resolve this, contact a Gas Safe registered engineer. The pilot lights are not an issue with newer boiler models.


  • Many problems can occur with boilers, and should be addressed by qualified engineers.
  • Boiler leaks must be addressed immediately.
  • The radiators may need to be bled if there is no central heating.
  • Leakage can cause low boiler pressure. This can be fixed by opening the filling loop.
  • Boiler kettling can produce a lot of noise, and may require the system to be cleaned or a part replaced.
  • You can thaw frozen condensate pipes using warm water.
  • If the thermostat is too far from the boiler or runs out of batteries, a boiler might not be able to respond.
  • A boiler engineer should be consulted if there is a problem with central heating or hot water.
  • An engineer can diagnose if a boiler is constantly switching on and will advise you if it needs to be replaced or if the boiler should be completely rebuilt. Sometimes, this can be more cost-effective.
  • Boilers can make a variety of distracting sounds, including gurgling or humming.
  • Do not attempt to repair any part yourself. It is safer to have an engineer fix any problems.