How often should my boiler be serviced, and when?

Most gas boilers should be serviced once a year by a Gas Safe registered engineer, with the first service about 12 months after the boiler was fitted. If yours has gone longer than that, it is worth booking one now, before the coldest weeks arrive and the boiler is working its hardest.

Below we cover why once a year is the usual answer, the best time to book, what changes for landlords, and the signs that mean you shouldn't wait. A service is a job for a qualified engineer, but there are a few simple things you can safely keep an eye on in between.

Why once a year is the usual answer

Every time a gas boiler fires, it wears parts a little and leaves deposits on the burner and heat exchanger (the part that passes heat from the flame into your heating water). A yearly service catches that wear before it causes a breakdown.

The Energy Saving Trust recommends a service every year by a Gas Safe registered engineer. Boiler makers say the same. Vaillant, for example, says a yearly service by a Gas Safe engineer helps keep its guarantee in place after the first year.

Your boiler warranty depends on it

Most manufacturers' warranties on new boilers ask for a service every 12 months. If the boiler breaks down and there is no record of a recent service, the manufacturer may refuse a free repair.

So keep the paperwork from every service, or a photo of it on your phone. Each time we service a boiler you get a written report, which gives you that record. If you're not sure what your warranty asks for, check the guarantee paperwork or the maker's website.

When in the year is best to book

Any time of year is fine if it's roughly 12 months since the last service, but late summer and early autumn are the easiest. The boiler hasn't had months of heavy use yet, and if the engineer finds a worn part, there is time to replace it before you need the heating every day.

One of our customers told us that having their boiler serviced late every summer "has prevented us from needing repairs during the rest of the year, especially during autumn and winter." Another said they have always had theirs done "by early autumn".

If your service is overdue and winter is close, don't wait for spring. Booking now still gives you the safety checks and a chance to fix a small fault before a cold-night breakdown.

Older boilers still need a yearly service

An older boiler often needs its service more, not less, because parts wear and seals harden over the years. A service won't make an old boiler new, but it will show whether it is still running safely and whether a part is close to failing. If an engineer finds one, you should be told what it is and what your options are, so you can plan a repair or replacement rather than having one forced on you.

If you rent the home out

Landlords have a legal duty to have every gas appliance in a rented home checked for safety every 12 months by a Gas Safe registered engineer. This is the gas safety check, and the record of it is often called a CP12 or gas safety certificate. The Health and Safety Executive says landlords must give existing tenants a copy within 28 days of the check, give new tenants a copy before they move in, and keep each record for at least two years.

A gas safety check is not the same as a service. The check confirms the appliances are safe to use, while a service also looks at the boiler's working parts and cleans them where needed. Many landlords have both done in one visit. Our gas services include landlord gas safety certificates.

Signs you shouldn't wait for the next service

Book a visit straight away, whatever the date of your last service, if you notice:

• a yellow or orange flame where you can see the flame, instead of a crisp blue one

• soot, or black or brown marks, on or around the boiler

• the boiler regularly locking out, or showing a fault code it didn't before

• water dripping from the boiler or the pipes underneath it

• new banging, whistling or gurgling noises

Carbon monoxide is a poisonous gas that can come from a faulty or badly maintained boiler. You can't see it or smell it. The NHS lists headaches, dizziness, feeling sick, tiredness and breathlessness as symptoms, often easing when you go outside. If you think your boiler could be leaking carbon monoxide, stop using it, get fresh air and call the National Gas Emergency number on 0800 111 999. A carbon monoxide alarm near the boiler gives you an early warning.

Never take the casing off the boiler yourself. The parts inside carry gas and electricity.

What you can check between services

There are a few safe things you can do yourself:

• check the pressure gauge on the front of the boiler every few weeks (on most boilers it should sit at about 1 to 1.5 bar when the heating is off, but check your boiler's manual)

• keep the space around the boiler clear

• test your carbon monoxide alarm when you test your smoke alarms

• in freezing weather, look at the plastic condensate pipe outside, which can freeze and stop the boiler

If the pressure keeps dropping, our guide to why a boiler keeps losing pressure explains the usual causes.

What happens on the day

The Energy Saving Trust says a service usually takes around 40 minutes to an hour, depending on the boiler's age and condition. The engineer checks how the boiler is burning, tests the flue and safety controls, looks at the pressure and the condensate pipe, and cleans parts where they need it. For a step-by-step look at each check, read what we test during a boiler service.

Our care plans spread the cost of a yearly service into monthly payments, if you'd rather not have to remember the date.

If it has been more than a year since your boiler was last looked at, BeeXpress Heating & Renewables can book you in for an annual service with one of our Gas Safe registered engineers. Find out more and book on our boiler servicing page.