Frequently asked questions

We've shared the answers to some of the most frequently asked questions about boilers, heating systems, servicing and maintenance. Can't find the answer? Contact us and we'll do our best to help.

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  • All FAQs
  • Winter Advice
  • Trouble Shooting
  • Boiler Servicing
  • Gas Safety
  • General Boiler Info
  • Parts Advice
  • ERP
  • uSense
  • Benchmark

All FAQs

Water Treatment Explained: How to Keep Your Heating System Healthy

Boiler servicing

Buying a new boiler is a big investment, and not taken lightly, whether it’s a distress purchase because your old boiler has broken down and can’t be repaired, you have extended your home and need a bigger boiler to cope with more radiators or you are concerned about your carbon footprint and want to be more energy efficient.

Carbon Monoxide (CO) Advice

Gas Safety

Carbon monoxide (CO) is a toxic gas produced by the incomplete combustion of fossil fuels including gas, oil, wood and coal used in boilers, engines, oil burners, gas fires, water heaters, gas ovens, solid fuel appliances and open fires.

It can occur when a gas appliance has been incorrectly fitted, badly repaired or poorly maintained. It can also occur if flues, chimneys or vents are blocked.

It is colourless, odourless and tasteless, so the best way to detect carbon monoxide is to fit a CO alarm.

Where can I find the serial number of my boiler?

Boiler servicing

The serial number can usually be found on the drop down panel on the front of the boiler. Some boilers have a tag underneath the boiler that slides out to reveal the serial number. If you can’t find your serial number, call Baxi Customer Support 0330 678 0917 with the name of your boiler and they will help you find it.

How Energy Efficient Is My Boiler?

ERP

As one of the biggest costs for householders in the UK, it is worth understanding how energy efficient your boiler is, and how much you could save if you replaced it with a new high efficiency model.

In April 2018, the Building Regulations changed again, requiring all new boilers to be at least ErP 92% efficient.

What To Do If My Boiler Keeps Losing Pressure

General boiler info

The pressure on your boiler can go up or down for different reasons. Whether you have high or low boiler pressure, we explain how to adjust it and what to do if your boiler keeps losing pressure.

How Do I Maintain a Boiler Flue in the Ceiling?

General boiler info

If you live in a property that has a boiler flue which cannot be inspected because it is hidden behind a wall or ceiling, you need to install an inspection hatch.

Top Tips for Maintaining Your Boiler

General boiler info

Your boiler is a box that brings gas, electricity and water together to heat up water for your taps and your central heating system.

What Is a Condensing Boiler?

General boiler info

The difference between an old non-condensing boiler and a new condensing model is the amount of useable heat it produces from the fuel it burns.

What Do Baxi Error Codes E133 or E28 Mean?

Trouble shooting

If your boiler has shut down and is showing error code E133 or E28, then your condensate pipe may be frozen.

Can I Run a Bath and Shower At the Same Time?

General boiler info

If you have a hot water storage cylinder, usually found in the airing cupboard, you should be able to run a bath and have a shower at the same time.

Boiler Plus What does it mean to you?

General Boiler Info

The part of the Building Regulations that deals with central heating boilers is undergoing the biggest change since the introduction of condensing boilers in 2005.  The change, commonly known as Boiler Plus, affects you when your old boiler is replaced, or you have a new boiler installed where there wasn’t one before.

The new law becomes effective on 6 April 2018 and applies to homes in England only.

Which Baxi Boiler Do I Have?

General boiler info

The easiest way to find out which Baxi boiler you have is by looking at the instructions that came with it.  It is always worth keeping these in a safe place, because they also include the Benchmark Checklist that your installer should have carried out when they fitted the boiler and also the boiler’s service history, which should be completed by the engineer when they carry out your annual service.

However, if you no longer have the instruction booklet you can find the serial number here.

Why should I consider replacing my boiler?

General boiler info

Most people only replace their boiler when it breaks down. However, there are still a number of benefits to upgrading to a modern high efficiency gas boiler such as better efficiency, better reliability or having different hot water needs after an extension to your house.

Read about the top benefits to replacing your boiler here.

Are Baxi Customer Support Engineers Gas Safe Registered?

Gas Safety

Yes, our nationwide network of Baxi Customer Support engineers are employed by Baxi and are Gas Safe registered.

What Do Baxi Error Codes Mean?

Trouble shooting

If your boiler develops a problem, it will often display an error code on the control panel that will help you or your Gas Safe registered installer identify what went wrong.

How to Reset a Baxi Boiler

Trouble shooting

If your boiler needs to be reset, these videos show you how, whether your boiler has a dedicated reset button, an ON/OFF/SELECTOR switch or a thermostat control knob.

How Does a System Boiler Work?

General boiler info

A system boiler, or sealed system, is a great option if you have more than one bathroom or your household has a high demand for hot water.

How Does a Heat Only Boiler Work?

General boiler info

Heat only boilers are also known as conventional, traditional, open vent or regular boilers.

What Are the Different Types of Boilers?

General boiler info

We explain about the different types of boiler and their pros and cons, so you can make an informed decision on which type of boiler you need when you come to replace yours.

What should the pressure gauge on my boiler be reading?

Trouble Shooting

The normal operating water pressure for your boiler and central heating system is between 1.0 and 2.0 bar. If the pressure drops below 1.0 bar, you need to repressurise it. If the pressure goes above 3.0 bar, you will see water coming from the pressure relief valve (usually on an outside wall). You can reduce the pressure by bleeding a radiator or draining some water out of the system using a drain point, usually found underneath a radiator.

What Is a Gas Safety Certificate?

Gas Safety

Under The Gas Safety (Installation and Use) Regulations 1998, owners of residential rented properties must arrange a gas safety check by a Gas Safe registered engineer for all pipework, appliances and flues in each of the properties which the landlord owns and provides for tenants to use.

Where Is It Safe to Install a Boiler?

General boiler info

You can have your boiler installed safely in most rooms, or even the loft. There are, however a few things to consider.

How to bleed your radiators

Trouble Shooting

If you have cold spots at the top of your radiators, it means that there is trapped air that needs to be removed so your radiators will heat your room efficiently.

Follow our 8 simple steps to on how to bleed a radiator here. 

How Does a Combi Boiler Work?

General boiler info

Combi, or combination boilers are the most popular type of domestic boiler sold in the UK.

How Do I Maintain the Pilot Light?

Trouble Shooting

If you have an older boiler (SEDBUK Band G), you should regularly check its pilot light, a small naked flame inside the boiler that you can see through a small hole covered by glass.

What Is a Back Boiler?

General boiler info

Back boilers (also known as back boiler units or BBUs) became popular in 1966 with the launch of the original Baxi Bermuda. A back boiler is a small, compact boiler fitted at the back of an open fireplace hearth. It sits behind a gas fire and provides hot water and central heating to the property. 

Click to find out everything you need to know about replacing a back boiler.

Annual boiler service

Boiler servicing

The law requires that all servicing and gas safety checks are made by a Gas Safe registered engineer and an annual service can make all the difference in reliability, efficiency and household bills. If your boiler is still under warranty, having an annual service is a condition of the warranty. Always ask to see the engineer’s Gas Safe ID.

Baxi Genuine Parts

Parts Advice

It might be difficult to tell the difference between a counterfeit part being installed into your boiler and a genuine part, but this could make a real difference to the running of your home heating system.

We recommend always asking your installer to use Baxi Genuine Parts, because they have been tested and approved for use in Baxi boilers.

How Old Is My Baxi Boiler?

General boiler info

To find out how old your boiler is, visit the official industry database Fill in details of your boiler and the dates when manufacture of that model began and ended will be displayed. You can search for all brands and models of boilers in this database. Or you can look at your boiler’s serial number.

This can usually be found on the drop down panel on the front. The serial number has all the information needed for us to tell you when your boiler was manufactured. Contact us with the details.

How to tell if the condensate pipe has frozen

Winter Advice

In most cases, the boiler will display an error code. For example, on most Baxi boilers, the error code will be E133 or E28. The display will alternate between E1 and 33.

How to tell if your condensate pipe is likely to freeze?

Winter Advice

Check to see if your condensate pipe runs along the outside of a wall at any point. The condensate pipe is a small, usually white, plastic pipe that comes out of the bottom of your boiler. It carries the ‘condensate’, which is the liquid produced when all the heat has been taken out of the gas that has burned to provide heating and hot water, to a drain.

Usually, the condensate pipe runs from the boiler to a drain under a sink, but in some cases, it may have been routed through the wall and into an external drain. The part of the pipe that is outside is most likely to freeze when temperatures start to plummet.


If your boiler is located in an unheated part of the house, for example in the garage or out-house, you should treat the condensate pipe as if it was outside. 

How Often Should I Have My Boiler Serviced?

Boiler servicing

Getting your boiler serviced every year is a bit like getting your car serviced. The law requires that all servicing and gas safety checks are made by a Gas Safe registered engineer and an annual service can make all the difference in reliability, efficiency and household bills. If your boiler is still under warranty, having an annual service is a condition of the warranty. Always ask to see the engineer’s Gas Safe ID.

Do I Need a Carbon Monoxide Detector for a Gas Boiler?

Gas Safety

For you and your family's safety, it is advisable to fit a carbon monoxide alarm in each room in your home that has a gas appliance or solid fuel heating.

Why is my boiler pressure high?

Trouble Shooting

If your boiler pressure is too high, it could be because a radiator has been removed, for example, while decorating a room, and the system was over-filled when it was replaced. If the water pressure continues to be high after bleeding the radiators, please call your heating engineer, or Baxi Customer Support on 0330 678 0917 to check the system is safe to use.

What’s wrong with my boiler? Try our basic boiler checks

Trouble Shooting

This five part basic checks video series can help you identify and repair basic boiler faults, problems, issues and error codes, helping you save time and money.

Click to view our videos. 

How to thaw a frozen condensate pipe

Winter Advice

It is quite simple to thaw the pipe and get your boiler up and running again. We explain how to do it below and advise how you can prevent it from freezing again.

What is Benchmark?

Benchmark

Benchmark is a nationally recognised scheme that gives manufacturers and installers the responsibility for ensuring best practice for the installation, commissioning and servicing of domestic heating and hot water products, in accordance with the Building Regulations in England and Wales. 

How do I reset my boiler?

Trouble Shooting

If your boiler needs to be reset, our videos show you how, whether your boiler has a dedicated reset button, an ON/OFF/SELECTOR switch or a thermostat control knob.

Click to watch our videos for more guidance.

How do I top up the water pressure?

Trouble Shooting

Sometimes boilers need to be repressurised. This is quite normal and you can repressurise your boiler yourself. Our videos show you how, whether you have a rigid or a flexible filling loop, or Easy-Fill permanent filling link.

How to prevent the condensate pipe from freezing again

Winter Advice

Once the pipe is thawed and the boiler has been successfully re-started, you can lag the pipe with waterproof and weatherproof lagging to help prevent it re-freezing. Click to watch our video.

Winter Advice

How to tell if the condensate pipe has frozen

Winter Advice

In most cases, the boiler will display an error code. For example, on most Baxi boilers, the error code will be E133 or E28. The display will alternate between E1 and 33.

How to tell if your condensate pipe is likely to freeze?

Winter Advice

Check to see if your condensate pipe runs along the outside of a wall at any point. The condensate pipe is a small, usually white, plastic pipe that comes out of the bottom of your boiler. It carries the ‘condensate’, which is the liquid produced when all the heat has been taken out of the gas that has burned to provide heating and hot water, to a drain.

Usually, the condensate pipe runs from the boiler to a drain under a sink, but in some cases, it may have been routed through the wall and into an external drain. The part of the pipe that is outside is most likely to freeze when temperatures start to plummet.


If your boiler is located in an unheated part of the house, for example in the garage or out-house, you should treat the condensate pipe as if it was outside. 

How to thaw a frozen condensate pipe

Winter Advice

It is quite simple to thaw the pipe and get your boiler up and running again. We explain how to do it below and advise how you can prevent it from freezing again.

How to prevent the condensate pipe from freezing again

Winter Advice

Once the pipe is thawed and the boiler has been successfully re-started, you can lag the pipe with waterproof and weatherproof lagging to help prevent it re-freezing. Click to watch our video.

Trouble Shooting

What Do Baxi Error Codes E133 or E28 Mean?

Trouble shooting

If your boiler has shut down and is showing error code E133 or E28, then your condensate pipe may be frozen.

What Do Baxi Error Codes Mean?

Trouble shooting

If your boiler develops a problem, it will often display an error code on the control panel that will help you or your Gas Safe registered installer identify what went wrong.

How to Reset a Baxi Boiler

Trouble shooting

If your boiler needs to be reset, these videos show you how, whether your boiler has a dedicated reset button, an ON/OFF/SELECTOR switch or a thermostat control knob.

What should the pressure gauge on my boiler be reading?

Trouble Shooting

The normal operating water pressure for your boiler and central heating system is between 1.0 and 2.0 bar. If the pressure drops below 1.0 bar, you need to repressurise it. If the pressure goes above 3.0 bar, you will see water coming from the pressure relief valve (usually on an outside wall). You can reduce the pressure by bleeding a radiator or draining some water out of the system using a drain point, usually found underneath a radiator.

How to bleed your radiators

Trouble Shooting

If you have cold spots at the top of your radiators, it means that there is trapped air that needs to be removed so your radiators will heat your room efficiently.

Follow our 8 simple steps to on how to bleed a radiator here. 

How Do I Maintain the Pilot Light?

Trouble Shooting

If you have an older boiler (SEDBUK Band G), you should regularly check its pilot light, a small naked flame inside the boiler that you can see through a small hole covered by glass.

Why is my boiler pressure high?

Trouble Shooting

If your boiler pressure is too high, it could be because a radiator has been removed, for example, while decorating a room, and the system was over-filled when it was replaced. If the water pressure continues to be high after bleeding the radiators, please call your heating engineer, or Baxi Customer Support on 0330 678 0917 to check the system is safe to use.

What’s wrong with my boiler? Try our basic boiler checks

Trouble Shooting

This five part basic checks video series can help you identify and repair basic boiler faults, problems, issues and error codes, helping you save time and money.

Click to view our videos. 

How do I reset my boiler?

Trouble Shooting

If your boiler needs to be reset, our videos show you how, whether your boiler has a dedicated reset button, an ON/OFF/SELECTOR switch or a thermostat control knob.

Click to watch our videos for more guidance.

How do I top up the water pressure?

Trouble Shooting

Sometimes boilers need to be repressurised. This is quite normal and you can repressurise your boiler yourself. Our videos show you how, whether you have a rigid or a flexible filling loop, or Easy-Fill permanent filling link.

Boiler Servicing

Water Treatment Explained: How to Keep Your Heating System Healthy

Boiler servicing

Buying a new boiler is a big investment, and not taken lightly, whether it’s a distress purchase because your old boiler has broken down and can’t be repaired, you have extended your home and need a bigger boiler to cope with more radiators or you are concerned about your carbon footprint and want to be more energy efficient.

Where can I find the serial number of my boiler?

Boiler servicing

The serial number can usually be found on the drop down panel on the front of the boiler. Some boilers have a tag underneath the boiler that slides out to reveal the serial number. If you can’t find your serial number, call Baxi Customer Support 0330 678 0917 with the name of your boiler and they will help you find it.

Annual boiler service

Boiler servicing

The law requires that all servicing and gas safety checks are made by a Gas Safe registered engineer and an annual service can make all the difference in reliability, efficiency and household bills. If your boiler is still under warranty, having an annual service is a condition of the warranty. Always ask to see the engineer’s Gas Safe ID.

How Often Should I Have My Boiler Serviced?

Boiler servicing

Getting your boiler serviced every year is a bit like getting your car serviced. The law requires that all servicing and gas safety checks are made by a Gas Safe registered engineer and an annual service can make all the difference in reliability, efficiency and household bills. If your boiler is still under warranty, having an annual service is a condition of the warranty. Always ask to see the engineer’s Gas Safe ID.

Gas Safety

Carbon Monoxide (CO) Advice

Gas Safety

Carbon monoxide (CO) is a toxic gas produced by the incomplete combustion of fossil fuels including gas, oil, wood and coal used in boilers, engines, oil burners, gas fires, water heaters, gas ovens, solid fuel appliances and open fires.

It can occur when a gas appliance has been incorrectly fitted, badly repaired or poorly maintained. It can also occur if flues, chimneys or vents are blocked.

It is colourless, odourless and tasteless, so the best way to detect carbon monoxide is to fit a CO alarm.

Are Baxi Customer Support Engineers Gas Safe Registered?

Gas Safety

Yes, our nationwide network of Baxi Customer Support engineers are employed by Baxi and are Gas Safe registered.

What Is a Gas Safety Certificate?

Gas Safety

Under The Gas Safety (Installation and Use) Regulations 1998, owners of residential rented properties must arrange a gas safety check by a Gas Safe registered engineer for all pipework, appliances and flues in each of the properties which the landlord owns and provides for tenants to use.

Do I Need a Carbon Monoxide Detector for a Gas Boiler?

Gas Safety

For you and your family's safety, it is advisable to fit a carbon monoxide alarm in each room in your home that has a gas appliance or solid fuel heating.

General Boiler Info

What To Do If My Boiler Keeps Losing Pressure

General boiler info

The pressure on your boiler can go up or down for different reasons. Whether you have high or low boiler pressure, we explain how to adjust it and what to do if your boiler keeps losing pressure.

How Do I Maintain a Boiler Flue in the Ceiling?

General boiler info

If you live in a property that has a boiler flue which cannot be inspected because it is hidden behind a wall or ceiling, you need to install an inspection hatch.

Top Tips for Maintaining Your Boiler

General boiler info

Your boiler is a box that brings gas, electricity and water together to heat up water for your taps and your central heating system.

What Is a Condensing Boiler?

General boiler info

The difference between an old non-condensing boiler and a new condensing model is the amount of useable heat it produces from the fuel it burns.

Can I Run a Bath and Shower At the Same Time?

General boiler info

If you have a hot water storage cylinder, usually found in the airing cupboard, you should be able to run a bath and have a shower at the same time.

Boiler Plus What does it mean to you?

General Boiler Info

The part of the Building Regulations that deals with central heating boilers is undergoing the biggest change since the introduction of condensing boilers in 2005.  The change, commonly known as Boiler Plus, affects you when your old boiler is replaced, or you have a new boiler installed where there wasn’t one before.

The new law becomes effective on 6 April 2018 and applies to homes in England only.

Which Baxi Boiler Do I Have?

General boiler info

The easiest way to find out which Baxi boiler you have is by looking at the instructions that came with it.  It is always worth keeping these in a safe place, because they also include the Benchmark Checklist that your installer should have carried out when they fitted the boiler and also the boiler’s service history, which should be completed by the engineer when they carry out your annual service.

However, if you no longer have the instruction booklet you can find the serial number here.

Why should I consider replacing my boiler?

General boiler info

Most people only replace their boiler when it breaks down. However, there are still a number of benefits to upgrading to a modern high efficiency gas boiler such as better efficiency, better reliability or having different hot water needs after an extension to your house.

Read about the top benefits to replacing your boiler here.

How Does a System Boiler Work?

General boiler info

A system boiler, or sealed system, is a great option if you have more than one bathroom or your household has a high demand for hot water.

What Are the Different Types of Boilers?

General boiler info

We explain about the different types of boiler and their pros and cons, so you can make an informed decision on which type of boiler you need when you come to replace yours.

Where Is It Safe to Install a Boiler?

General boiler info

You can have your boiler installed safely in most rooms, or even the loft. There are, however a few things to consider.

How Does a Combi Boiler Work?

General boiler info

Combi, or combination boilers are the most popular type of domestic boiler sold in the UK.

What Is a Back Boiler?

General boiler info

Back boilers (also known as back boiler units or BBUs) became popular in 1966 with the launch of the original Baxi Bermuda. A back boiler is a small, compact boiler fitted at the back of an open fireplace hearth. It sits behind a gas fire and provides hot water and central heating to the property. 

Click to find out everything you need to know about replacing a back boiler.

How Old Is My Baxi Boiler?

General boiler info

To find out how old your boiler is, visit the official industry database Fill in details of your boiler and the dates when manufacture of that model began and ended will be displayed. You can search for all brands and models of boilers in this database. Or you can look at your boiler’s serial number.

This can usually be found on the drop down panel on the front. The serial number has all the information needed for us to tell you when your boiler was manufactured. Contact us with the details.

How Does a Heat Only Boiler Work?

General boiler info

Heat only boilers are also known as conventional, traditional, open vent or regular boilers.

Parts Advice

Baxi Genuine Parts

Parts Advice

It might be difficult to tell the difference between a counterfeit part being installed into your boiler and a genuine part, but this could make a real difference to the running of your home heating system.

We recommend always asking your installer to use Baxi Genuine Parts, because they have been tested and approved for use in Baxi boilers.

ERP

How Energy Efficient Is My Boiler?

ERP

As one of the biggest costs for householders in the UK, it is worth understanding how energy efficient your boiler is, and how much you could save if you replaced it with a new high efficiency model.

In April 2018, the Building Regulations changed again, requiring all new boilers to be at least ErP 92% efficient.

uSense

Benchmark

What is Benchmark?

Benchmark

Benchmark is a nationally recognised scheme that gives manufacturers and installers the responsibility for ensuring best practice for the installation, commissioning and servicing of domestic heating and hot water products, in accordance with the Building Regulations in England and Wales. 

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