Vaillant boiler help
Plain-English help for your Vaillant boiler: fault codes, diverter valve problems and boiler pressure.
Sort your Vaillant boiler problem
Pick the guide that matches what your Vaillant boiler is doing. Each one explains what's going on, what's safe to check yourself, and when to book a Gas Safe registered engineer.
If you ever smell gas, stop and call the Gas Emergency Services line on 0800 111 999. Never attempt gas repairs yourself.
Smart Plan cover terms at a glance
The terms behind every cover answer below. Smart Plan is a service plan from UK Boiler Company Ltd (company 09078640), not insurance, so it does not carry insurance-style protections.
- Cover limits per 12-month period: up to £500 on most modules, £225 per appliance, and boiler and central heating up to £500 when the boiler is under 7 years old or up to £200 when it is 7 years or older. You pay any shortfall above the limit.
- Cover-plan call-outs run Monday to Friday, 08:00 to 18:00. If your boiler fails outside those hours, the earliest we can attend is the next working day.
- A £95 call-out fee, paid in advance, applies in defined cases: any call-out in the first 30 days of a new agreement, issues that fall under an exclusion, visits where our engineer cannot get access, and early annual-service requests. The first 30 days is a fee window, not a gap in cover.
- An annual service is not automatically included in cover, so arrange one separately unless your product includes it.
- One-off works run 09:00 to 17:00 and do not carry a workmanship guarantee, so they are not the same as cover.
- Billing is monthly, but a 12-month agreement period begins once you use a service. A 14-day cooling-off period applies from sign-up and ends if a service is carried out inside it.
- Leaving during the agreement period costs the remaining monthly payments, or 75% of the outstanding balance as a one-off.
- Exclusions apply and are set out in our terms and conditions.
Vaillant boiler FAQs
Where do I find the fault code on my Vaillant boiler?
The fault code shows on the boiler's own display, normally as an F followed by two digits, such as F22 or F75. On most Vaillant combi boilers the display sits on the front panel or behind the drop-down flap. Write the exact code down before you reset anything, because it tells a Gas Safe registered engineer where to start looking.
What pressure should a Vaillant boiler be set to?
Most Vaillant boilers sit at roughly 1 to 1.5 bar when the system is cold, and the reading rises a little as the heating warms up. Check the manual for your specific model, because the recommended range varies. If the pressure keeps dropping after you top it up, the system is losing water somewhere, so book a Gas Safe registered engineer rather than refilling it again and again.
What are the signs of a Vaillant diverter valve problem?
The usual sign is heating and hot water behaving as though they are stuck together: hot water only when the heating is on, radiators warming up when you run a tap, or hot water that turns lukewarm. The diverter valve sends heated water either to your taps or to your radiators, so when it sticks, one of them loses out. That is engineer work, not a DIY fix.
Does a Vaillant boiler need an annual service?
Yes. Vaillant recommends a service every 12 months, and most manufacturer warranties require one to stay valid, so keep the paperwork. A service checks combustion, seals, pressures and safety devices, which is how small faults get caught before they stop your heating in winter. Any Gas Safe registered engineer can carry out the service, and an annual service is not automatically part of a cover plan.
How long is the warranty on a Vaillant boiler?
Warranty length depends on the model and on registering the boiler with Vaillant inside the set window, so check the paperwork that came with it. An annual service by a Gas Safe registered engineer is normally a condition too, and some registered installer schemes extend the period. Vaillant publishes the current terms on its own site. Once the warranty ends, a Smart Plan cover plan is one way to handle repair costs.
Who is allowed to repair my Vaillant boiler?
Only a Gas Safe registered engineer may carry out gas work on your Vaillant boiler, because gas work is legally restricted to registered engineers. You can safely read the fault code on the display, check the pressure gauge, and confirm the gas and electricity supplies are on. Anything touching the gas supply, the combustion side or internal components has to be left to a registered engineer.
Call us today
Customer service
0333 772 6247New customers
0333 772 6247Write to us
By email
hello@smart-plan.comBy post
2nd Floor, Melrose House
42 Dingwall Road
Croydon
CR0 2NE