Worcester Bosch combi boilers are the pride of many British homes — reliable, efficient, and built to last. But like any bit of hardworking kit, even the best need a bit of TLC to keep ticking over smoothly.
If you’re wondering what really happens during a boiler service (beyond us disappearing into your airing cupboard for an hour), here’s a full, honest breakdown. No vague checklists. No fluff. Just a proper explanation of what we actually do when servicing your Worcester Bosch combi boiler.
Why your Worcester needs an annual service
Even if your heating’s been working fine, your boiler still benefits massively from a yearly check-up.
Servicing:
- Keeps your boiler running efficiently, so you don’t spend more than you need to on gas
- Helps us spot and fix small issues before they become big, expensive ones
- Keeps your manufacturer warranty valid (Worcester Bosch insist on it annually)
- Ensures your boiler is safe to use and not leaking carbon monoxide
A small investment each year keeps your home warm, your bills lower, and your boiler warranty intact.
What we actually do on the day
Whether you’ve got a Worcester Bosch Greenstar i, Greenstar 4000, Life, Style or Compact — the basics of the service are the same. Here’s what our engineers do during a standard service visit
1. Visual inspection
We start with a proper look over the boiler, checking:
- For signs of corrosion, leaks, or damage
- That the flue is safely installed and not blocked (inside and outside)
- That there are no error codes or lockouts showing
- That the boiler case seals are intact and the area is safe to work in
This step gives us an overview before diving into the technical stuff.
2. Test gas pressure and fan pressure
We check:
- Gas inlet pressure (to make sure the boiler is getting the right flow)
- Burner working pressure (while it’s running)
- And we also carry out a fan pressure test
The fan pressure test is a crucial one. It ensures combustion gases are being safely expelled and the boiler is drawing in the correct air-to-gas ratio. It also tells us if the fan is showing signs of wear or weakness, which could affect efficiency or safety.
3. Strip down & clean the burner and heat exchanger
(Only when needed)
Worcester Bosch boilers are built to a very high standard, and in most cases, don’t need to be stripped down and cleaned every year. We typically carry this out every four years, or sooner if your combustion readings or seal condition suggest it’s required.
If it’s needed, we:
- Remove the burner and combustion chamber cover
- Clean the main heat exchanger
- Inspect and clean the ignition electrodes and flame sensor
- Check the condition of the burner mesh
Important to note: this type of deep service may require replacement of seals and electrodes, which can incur additional costs. If that’s the case, we’ll always let you know before going ahead, and explain what’s needed and why.
4. Clean the condensate trap
The condensate trap collects acidic water from the combustion process. We:
- Remove it
- Flush it through
- Check for blockages or deterioration
- Refit and test
A blocked condensate trap can cause the boiler to shut down, especially in winter.
5. Expansion vessel & safety checks
We check:
- The pressure in the expansion vessel, topping it up if needed
- That the pressure relief valve is operating correctly and not leaking
- All internal safety features are functioning properly, such as flame detection and thermostat cut-outs
These components keep your boiler safe if something goes wrong.
6. Clean the magnetic filter (if fitted)
If you’ve got a magnetic filter (like a MagnaClean), we:
- Remove the magnet
- Clean the inside of sludge and debris
- Refit and repressurise
If you don’t have a magnetic filter, we may recommend installing one — it’s one of the best ways to protect your system from sludge build-up.
7. Combustion analysis using flue gas analyser
We insert a flue gas analyser into the flue and take readings of:
- CO (carbon monoxide)
- CO₂ (carbon dioxide)
- Oxygen and excess air
- Boiler efficiency and performance
These readings are compared to Worcester Bosch specifications to make sure your boiler is burning cleanly and safely. If the numbers are off, we’ll adjust the gas valve accordingly.
8. System pressure check and top-up
We check your system pressure and top it up to the correct level, usually around 1.5 bar when cold. If it’s regularly dropping, that could indicate a leak or faulty valve, which we’ll advise you on.
9. Check boiler controls and settings
We’ll test your heating and hot water controls to make sure:
- Timers, thermostats and smart controls are working correctly
- The boiler responds as it should when called for heat
- Your settings are optimal for comfort and energy savings
If you’re using a Comfort+ II RF or Bosch EasyControl, we’ll also check the connectivity and signal strength.
10. Complete your service record and leave you a full report
We update your boiler’s service history (paper or digital) and provide you with a full report. This includes:
- And a record to keep your warranty valid
- The checks completed
- Any recommendations
How long does it take?
A standard Worcester Bosch combi boiler service takes around 45 minutes to an hour. If we’re doing a full strip-down (on a four-year cycle or as needed), it may take slightly longer.
We don’t rush, and we don’t cut corners.
How much does it cost?
Our standard service charge is £120, including VAT.
If you’re signed up to one of our Cosy Care Plans, your annual boiler service is included — no extra charge.
You’ll also benefit from:
- Priority breakdown response
- Peace of mind all year round
You can explore our plans here: View Cosy Care Plans
Ready to book your Worcester service?
We’re Worcester-accredited installers and service engineers, and we know these boilers inside and out. Whether you’ve got a Greenstar 4000 or a Classic i Combi, we’ll look after it properly.
Book online now:
Book an appointment Or call us on 0114 248 3011