Frequently asked questions

Why does my boiler bang?

If your boiler makes a banging noise when it is running it could be a few things.

The most likely is kettling, this sounds similar to the bubbling noise a kettle makes just before it finishes. A kettling boiler is a sign that either the flow is reduced (faulty pump) or there is a blockage.

If it is blocked it may be possible to flush the heat exchanger, the rest of the heating system is likely to need flushing also.

What's the best setting for a thermostat to save money?

Generally speaking anything above 19c will be adequate.

Older people will need greater than 22c as they have reduced movement.

Office workers often also need a higher temperature due to long periods of sitting still. Suggesting they do some star jumps every twenty minutes has never been found funny by them.

How can I make the water hotter?

If you have a combination boiler it will most likely have a dial with a tap on it or a digital control for the same. The manual will have instructions on how to raise it.

If you have a cylinder it will have a thermostat either strapped externally or integrated internally. If it is the external type the dial will be obvious and can be turned by hand or with a small screwdriver. If it is integrated it is not recommended to open and manipulate yourself as it could have live terminals.

Why is the top of my radiator cold?

It is almost certainly just air trapped in the top, it needs to be vented with a radiator key.

Once you have done this you may need to re-pressurise your system.

Why doesn't my radiator work?

If the radiator was working and it was turned off over the summer it is very likely that the TRV pin has seized shut. This can be remedied easily but removing the plastic head and tapping down lightly with a hammer. You will see the pin raise up and the head can be replaced.

Why can I smell gas?

Although many things can smell like gas, it is a distinctive smell.

If you smell gas you should turn it off at the meter and call a registered gas installer.

If you think it is an emergency you should

Call free 0800 111 999 Open doors and windows Turn off gas at meter (unless the meter is in a cellar or basement) Don't use electric switches or naked flames

Why does the hot water take so long to come to the tap?

If you have a combination boiler it will need to warm up the heat exchanger before it can heat up the water. This takes time and can be reduced by turning on a pre-heat function.

If you have stored hot water and the outlet is a long way from the cylinder you can reduce the time by installing a return pump.

It could also be an indication of a fault, a passing shower mixer or internal diverter could manifest in that way.

Why is some of my house colder?

It is likely that the system needs balancing, this is required by the installer when a new boiler is fitted but for older systems it is quite common. As a system is worked on or the house changes over the years it can need adjusting.

See our guide in the how to section on balancing.

How do I pressurise my heating?

You will likely have a filling loop outside or inside the boiler, this needs to be correctly used to raise the pressure to 1-1.5bar.

Our how to guide takes you through the steps -

What is a good boiler?

The cheapest boiler installed on the cleanest system will outlast the most expensive boiler on the dirtiest system.

There are very few bad boilers on the market now, it is so competitive that there is little room for error by manufacturers.

Generally as long as the heat exchanger has copper or stainless steel waterways and it can accept modulating control then it will last.

You want the boiler that has the best mix of

There are some boilers which are overpriced and there are boilers that are undervalued by the public. Check out our no holds barred boiler review here -

How often should I service my boiler?

If you are a landlord then you legally have to have an annual gas safety check in which any gas appliance, the gas pipes, meter, and other safety aspects are checked by a registered gas installer. Following this you must present a valid CP12 certificate to your tenants and retain one for your own records.

If you are a homeowner it is recommended you follow the same protocol. It is also necessary to have the boiler serviced annually to maintain the warranty.

Can I service my boiler myself?

If you are a registered gas installer and the have the relevant qualifications then yes.

If you aren't an RGI and the work you are carrying out to the boiler does not involve removing any covers or interrupting the gas supply then yes. In days gone by people would hoover or sweep underneath the open flued fire or boiler to remove cat hair or dust.

In reality there is almost no likelihood that you could safely work on our own gas appliance, it is extremely dangerous and illegal. Unregistered individuals working on gas or gas appliances can face jail time for illegal work and although gas explosions are thankfully not common, they are devastating.

How much should a boiler service cost?

How much should a boiler service cost?

What qualifications do you need to work on boilers?

Other than being gas safe registered, the individual undertaking the work must hold the relevant module.

When you ask to see their Gas Safe card you can look on the back to see what they are allowed to work on.

If you want to check the engineer before they attend you can search on and search by company name or registration number which should be on their website or correspondence.

Why is my gas bill so high?

A high gas bill could be an indication of incorrectly set controls, a boiler calibrated poorly or even a gas leak.

It may also be that the boiler is quite old, a modern boiler and controls can dramatically reduce fuel usage.

How can I lower my gas bill?

Turning down the temperature of the boiler is one quick and easy way to lower your gas bill, especially if you have a condensing boiler. Leave the thermostat as normal (19-21c) and lower the boiler thermostat to 60-70c. This will increase the chance of condensing and improve fuel efficiency.

What's a good thermostat?

The bare minimum requirement for controls is to have a timer and thermostatic control of heating and hot water.

For combination boilers it is now required to have a modulating control for either load or weather, some kind of smart control or a flue heat recovery system.

What is a smart thermostat?

A smart thermostat is usually the term for an Internet connected system.

It isn't necessarily smarter than a non Internet controller except that it can be remotely accessed.

When should I put my heating on?

With the right controls you should never need to think about when to turn the heating on and off.

A correctly set programmer and thermostat will hold the heating off through the warmer months and only heat the home when needed.

What is the best setting for a trv?

If it is a well used area then leaving the trv set to full is fine.

If the room isn't used very often you can set the temperature as low as 1 or even the frost setting.

If the room is used but gets too hot you will need to practise and keep changing it lower until the room is the right temperature.

This can also be aided by balancing the system correctly.

Why is there water dripping outside the house near the boiler?

If it is coming from a copper pipe it could mean that the internal expansion vessel needs repairing or replacing.

If it is coming from a plastic pipe it may mean that the boiler condense is incorrectly installed or an overflow from a basin or toilet is to blame.

Corgi registered or Gas Safe?

Corgi has not been the regulatory body for gas in the U.K since April 2009.

Since then any operative working on gas must be registered with Gas Safe and hold the relevant qualifications.

Corgi does still exist and has some member schemes but they do not allow for their members to comply with the regulations.

What happens in a boiler service?

Many companies advertise a boiler "service" but really carry out nothing more than a safety check. Manufacturers sometimes say a full service is only recommended every other year but for most boilers it is advisable to check more than the gas pressure and flue gas emissions.

For a full service I would expect an engineer to not only check the inlet pressure or burner pressure and flue emissions but also remove the burner, check the heat exchanger, clean the condense route and check the delta T across the flow and return.

We have a checklist our engineers adhere to, to ensure the most comprehensive service is conducted.

Where is my stopcock?

You should have two stopcocks:

The first should be in the street or outside the property, this belongs to the water provider and is their responsibility.

The second will be inside your property, commonly it is under the kitchen sink or under the stairs but I have seen them in every conceivable part of a house. If you don't know and have recently moved in you can try tracing backwards from the cold tap in the kitchen or ask the previous owner, they will have used it at some point.

What's the best boiler?

The best boiler may be different in every home, there is no best boiler for every situation.

Your installer should be capable of selecting the right boiler to best suit your property and save the most in running and repair costs over its lifetime.

Who is responsible for the boiler in a rented house?

Unless otherwise agreed the boiler and all gas appliances are the responsibility of the landlord/s. They have a legal requirement to have them serviced and operational.

How do I tell of I have carbon monoxide poisoning?

If you feel dizzy or sick and have a gas appliance in the room you spend time in then you could have cO poisoning.

Open the doors and windows, turn the appliance off and seek professional help.

Our guide on carbon monoxide can give you more information -

How do I test my smoke alarm?

The alarm should have instructions on the front, generally holding the button for a few seconds until the alarm sounds.

Does my landlord have to service my boiler?

Your landlord has to give you a copy of a valid CP12 certificate within 12 months of the previous one.

Each gas company who provides the certificate must have visited the property and conducted specific tests to ascertain the safety of the installation and appliances.

Is my gas meter large enough?

Most people in their homes will have a U6 or equivalent meter, 6 indicates 6m3/hr of gas.

An easy calculation for finding the kw is m3x10.8 e.g 6x10.8=64.8

Your U6 meter is capable of providing a maximum of 64.8kw of appliances at one time.

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