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Boiler Not Working 15 Common Problems


Unfortunately, boiler systems slave away like donkeys in most homes with little to no appreciation. They deliver hot water and heating without fail all year long. And every year, you pay no attention to it until it finally gives up and leaves you high and dry in the winter cold.

Below are some common issues that could be causing your boiler breakdown along with their simple and quick fixes.

15 common boiler problems and how to fix them

  1. Is your boiler turned on?

This might seem like an obvious and patronizing statement, but it’s not. Boiler installation companies in the UK are always attending to home calls to fix broken boilers only to be greeted by boilers that are switched off – usually at the mains.

It could be someone in the house switched it off and forgot to tell you or the switch flipped during a power surge to protect your boiler from being fried. So probably your boiler isn’t broken down, it’s just switched off.

The fix to this problem is easy and quick – switch on the boiler. It will not cost you a dime.

  1. Boiler thermostat not working

It is common practice for governments worldwide to blame the poor and immigrants for their inadequacies. In the same way, boilers are held accountable for malfunctions and inefficiencies caused by their controllers.

If you have a modern boiler installed, chances are you don’t have to access the boiler to turn it on physically. While this is a welcomed convenience, it could be the source of your boiler problems. Inspect the thermostat to determine if it’s working as it should. Chances are your boiler is in tip-top shape and the thermostat isn’t.

How do you check if the thermostat is working?

  • Step 1: Check if it’s on, has working batteries and a full charge
  • Step 2: Ensure it is set to the optimal house temperature
  • Step 3: If it is a wireless thermostat, check your Wi-Fi connection. It should be strong and consistent
  • Step 4: Review the thermostat time settings to ensure that no standby options, vacation modes or unprecedented daily schedules have been programmed

How do you fix a faulty thermostat?

  • Replace its batteries and charge it to 100%
  • Erase all settings and set it to manual operation
  • If it gets confusing, refer to your boiler/thermostat manual
  1. Boiler not working? Check if the pressure is low

Boilers naturally lose pressure with time. There are several reasons why this happens, many of which are not a cause for alarm. If the boiler is not working because of low pressure, you can have it working in no time.

But how do you know low pressure is the cause of the boiler problems? Take a look at the boiler pressure gauge. The gauge should be reading 1 BAR and be in the green zone when it is off. When it’s running, the pressure will be slightly elevated but it should go back to normal when not in use.

How to repressurise your boiler

  • Step 1: Find the filling loop

The filling loop is located under the boiler amidst the pipework. It is usually a silver flexi pipe with one or two taps on.

  • Step 2: Adjust the pressure

In this case, you need to adjust the pressure upwards. To do this, open the black tap(s) to the 45-degree locking position. As you turn the taps the pressure should start to rise towards the 1 BAR mark.

  • Step 3: Once in the green zone, close the filling loop taps

Once the boiler pressure is back to the green zone, close the taps. Make sure you turn them completely to their initial position.

  1. Boiler pressure issues

Boiler pressure ensures the system is working efficiently and safely. Most boiler systems are sealed. They don’t have vents to handle contraction and expansions as the system changes between cold and hot. Instead, they rely on pressurisation to adjust to the changes.

As seen above, low boiler pressure causes boiler problems. But so does high boiler pressure. When the boiler gauge is above the green zone and reads pressure higher than 1.3 BAR, your boiler will malfunction. If not addressed urgently, you could end up spending a fortune on boiler and home repairs.

If high pressure is the problem, you need to release pressure from the system. You can do this by bleeding the boiler radiators. Like with low pressure, you should first turn the system off and allow it some time to cool.

Follow the steps below to ease the boiler pressure

  • Place a bowl under the radiator valve to catch any leaks
  • Use a radiator key to turn the valve anticlockwise. If you don’t have the key, use a flathead screwdriver
  • You will feel air escaping the system and then water
  • Monitor the pressure gauge. Once the pointer is back to the green zone, close the radiator valve
  1. Leaking boiler

Leaks inside or around the boiler system are a nightmare, mainly because of the mess they leave on floorboards and carpets. Moreover, the leaks will cause a drop in boiler pressure.

How do you check if you have a leaking boiler?

You can check for drips underneath the boiler or unexplained patches of water around the house. It would help if you also inspected the pipework around the house, paying close attention to the bends and joints in the pipes. Lastly, you could remove the boiler cover and check for signs of water leakage inside the system. However, we recommend leaving this latter inspection to an engineer.

How do you fix the leaking problem?

For this boiler problem, you will need to call a Gas Safe engineer to replace faulty parts in the system or secure leaks in the pipework. If the leak is internal and caused by a faulty part, you should consider replacing the boiler rather than getting stuck in an endless repair loop.

  1. No power to the boiler

If the boiler will not turn on and it seems like it’s dead, you most likely have an electrical problem. The most common cause is a faulty circuit board. To check if this is the problem;

How to check the problem

Turn the boiler on and off from the mains. You have to call in a Gas Safe engineer to help in diagnosing the problem. However, if the boiler is ‘dead’ along with your lights, kettle, TV and washing machine, you should call in an electrical engineer.

How to fix the problem

If the circuit board is the problem, then you will need to replace it. The replacement will cost a few hundred pounds. But if it’s a problem with the fuse, the repair is cheaper.

  1. Frozen condensate pipes

The condensate pipe runs from the boiler to the nearest wall accessing the outside. It transports condensation from the boiler and deposits it outside. Though the condensate is little and drips slowly from the pipe, it is vulnerable to freezing during winter.

A frozen condensate pipe blocks the system. The excess water, therefore, has no escape from the boiler. In response, the boiler shuts down to prevent a malfunction.

How to fix a frozen boiler

The quickest solution is to defrost the condensation pipe. To do this, pour warm water over the pipe until the ice melts. Once the ice is melted, turn on the boiler.

How to keep the condensation pipe from freezing

  • Check on the pipe regularly especially during winter.
  • Wrap the pipe in a cloth or foam to insulate the pipe and prevent future freezing.
  1. Radiator not heating up

If one or multiple radiators are not getting hot, then it’s unlikely that the problem is your boiler. The common cause is air or sludge buildup in the system. If the radiator is getting hot at the bottom, then you should bleed the radiator. Luckily the process is simple and doesn’t require an engineer to complete it successfully.

How to bleed the radiator

  • Before you start, turn off the boiler and allow it some time to cool. During the process, water will gush out of the system. When this happens, you don’t want it to be hot water.
  • Turn the bleed screw (it’s a square screw) to release water and air from the system. Place a container at the bottom to catch the sludge.
  • When you turn the bleed screw, first air will escape and then water.
  • When you are done, wipe down the water from the radiator to prevent rusting before you proceed to the next radiator.
  • Once all radiators are bled, turn the boiler back on.

If some radiators are not heating up, then they need balancing. You can also do this without the help of an engineer. The process involves adjusting radiator valves to ensure each is getting hot water.

If balancing and bleeding the radiators doesn’t solve the problem, then the problem is sludge build-up. You should call a Gas Safe engineer to remove the build-up using special chemicals or flushing the system.

  1. Boiler timer not working

When the boiler timer is working perfectly, when you turn on the heating, hot shower or tap, the boiler should give warm or hot water. If the timer is faulty, you will experience a range of problems including:

  • The boiler is operational but the radiators are cold
  • The boiler is not turning on
  • The boiler turns on and then goes off immediately
  • The heating is much colder or hotter than normal

However, the above symptoms could be caused by other faults as well. Symptoms specific to boiler timers include:

  • The boiler turns on an hour after or before the correct time
  • The thermostat doesn’t connect with the boiler timer to tell the boiler to turn on or off

Quick faulty timer fixes

Time settings – you should first check if the boiler time is right. If the clocks changed, then the time is incorrect. This could have happened during a recent electrical wiring project. Like clocks on mobile phones, boiler timers resent to midnight. This can explain why the boiler turns on randomly.

Power – if there’s no power to the boiler, the boiler won’t turn on. In this case, a blown fuse could be the problem. Replacing it could solve the problem. We recommend calling in an electrician or a Gas Safe engineer to handle the problem.

  1. Banging, whistling or rattling noises

Though hearing any of these noises can be annoying, they are a common homeowner experience. The type of noise the boiler makes can help you diagnose the problem.

Banging noises are caused by limescale build-up in the heat exchanger. The limescale blocks water flow and causes some water to boil and expand like in a kettle leading to banging noises.

Whistling noises can be caused by air trapped in the system. This noise is solved by releasing the air trapped in the system. Whistling noises can also be caused by a blockage or low water pressure.

How to fix the boiler noise problem

If the problem is caused by a limescale build-up, the solution is to use a treat the system with a chemical descaler.

  • Step 1: Turn off the boiler
  • Step 2: Add the chemical descaler into the expansion tank and let it settle for several days
  • Step 3: Drain and flush the system. Refill it once you’ve determined it’s clean

If it’s insufficient water pressure, re-pressurise the boiler as guided above.

  1. Pilot light keeps switching off

The pilot light is blue and is always on under the boiler. It is keeps going off then the boiler isn’t working. The common cause is a damaged thermocouple which is preventing gas supply from getting to the boiler. The draught caused might blow the pilot light.

In newer boilers, it’s rare to see the boiler turning off. But when they do, it is difficult to turn it back on. Before trying to turn the pilot light on, check the gas supply. Check if the gas stopcock is tightly on and confirm the boiler isn’t getting gas. Also, if the other gas appliances in the house aren’t working, you will have to call a gas supplier.

If you are confident relighting the pilot light, strictly follow instructions on the boiler manual. However, we recommend calling in a Gas Safe Engineer to handle the process.

  1. Have you paid your gas bill?

This reason sounds obvious as well, but it’s common. Homeowners take their boilers for granted to the extent they don’t pay attention to the gas bill. If the energy bill isn’t paid, the boiler will not work.

You probably forgot to pay the gas bill last month, or the energy company had a mishap. Either way, you should check.

  1. Boiler overheating

When a boiler overheats, it shuts down. Experts call this ‘boiler lockout’. Every boiler manufacturer incorporates this shutdown procedure in their design. The problem needs to be fixed fast.

What causes boiler overheating?

Removing the pressure release valve – these valves are designed to release pressure when the boiler gets hot and expands. The pressure is released via the PRV. But PRVs leak often. And instead of replacing the PRV, some engineers will seal or remove it to stop the leak. Doing this will cause the boiler to overheat or in worse cases explode.

Failed thermistor – thermistors work with the circuit boards. They inform the circuit boards of temperature demands. A faulty thermistor could lead to too much fuel supply, extremely hot water and overheating.

Limescale build-up in the heat exchanger – limescale are minerals from hard water. When limescale builds up, it causes a block in the system and creates hot spots. These hot spots lead to noise in the system and can also cause overheating when the boiler is on.

Blockages – the two common types of blockages are condensate pipe and heating sludge blockage. They both cause pressure build-up and create hot spots in the system.

Pump overheating – pumps should be warm and not hot. When it is too hot, there’s a good chance the internal parts are seized. A gentle tap may fix the problem. Other times, the pump needs to be disassembled, inspected and cleaned.

How to prevent boiler overheating;

  • Hot flush the system to remove heating sludge and limescale
  • Have an engineer install a scale reducer
  • Install a magnetic system filter
  • Install a boiler inhibitor to the system
  1. Boiler faulty parts

A boiler with faulty parts is dangerous. Boiler parts become less efficient with time and become faulty as well. Common parts that become faulty include oxygen depletion sensors, pressure release valves, thermostat, timers and PCBs.

The quickest fix to these faults is replacing the faulty items. Have a Gas Safe engineer perform the replacements.

  1. You have an old boiler

If your current boiler was installed a decade ago, it’s time to replace the boiler. Old boilers are susceptible to faults and aren’t as efficient as new boilers. Not replacing a boiler will only cost you money and eventually replace the boiler.

Brand new boilers come with labour warranties and help in lowering energy bills because of their efficiency. And even better, they make a home a safer space.

Which boiler brand is reliable from Valliant, Worcester, Ideal, Glow Worm and Baxi?

Each of the above boiler brands is excellent and only vary slightly from each other. When determining which boiler brand to choose, you should consider:

  • Price
  • Support
  • Reliability
  • Warranty

But generally, Worcester Bosch provides the best value for its price. If you need an oil boiler installed, you should call in a Gas Safe engineer.

Boiler still not working? Here’s what to do next

If the above quick fixes don’t work you should get in touch with us.

Compare the Boiler Market is a national boiler installation business that finds happiness in customer satisfaction. And since we operate online, our overheads are minimal and will translate into our customers making huge savings in boiler repair and installations.

Once you get in touch by filling in a form, we shall get back to you with recommendations of three of the best gas registered companies in the UK. You will compare the quotes and pick one that you prefer. The engineer will visit your home and help in diagnosing the problem.

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