On this page
- What does CE 207 mean on a Worcester Bosch boiler?
- Worcester bosch low pressure error: first checks
- How to top up pressure and clear CE 207
- CE 207 keeps coming back: what it usually means
- What you should not do
- Related Worcester codes and when to call an engineer
- Book a Worcester Bosch pressure fault repair
- Frequently asked questions
Key takeaways
- CE 207 is a low system pressure fault. The boiler stops to protect itself, it is not a gas fault.
- Check the pressure gauge with the boiler cold. Your Worcester user manual gives the correct cold pressure for your system, commonly around 1 to 1.5 bar.
- Topping up through the filling loop is a user-level task, but follow your model’s instructions and close the loop fully afterwards.
- If CE 207 comes back within days or weeks, look for leaks and check whether the pressure relief pipe outside is dripping. Then call an engineer.
- A pressure that rises high when the heating is on and drops low when cold often points to an expansion vessel problem, which is engineer work.
The Worcester Bosch CE 207 error is the low water pressure fault on Greenstar boilers: the boiler’s pressure sensor has detected that the water in your heating system has dropped too low for it to run safely, so it stops firing. If it happens once, topping the system back up to the pressure in your user manual using the filling loop usually clears it. If CE 207 keeps coming back, water is escaping somewhere, through a leak, the pressure relief valve or a failing expansion vessel, and the boiler needs a Gas Safe registered engineer.
This guide explains what the code means, how to check and top up safely, and how to tell a one-off pressure drop from a fault that will keep returning.
What does CE 207 mean on a Worcester Bosch boiler?
Worcester Bosch Greenstar combi and system boilers run on a sealed heating circuit, which needs a certain amount of water pressure to circulate properly and protect the heat exchanger. A pressure sensor inside the boiler monitors it constantly. When the pressure falls below the boiler’s minimum, the boiler blocks operation and shows CE 207 on the display, often with a flashing pressure or spanner symbol depending on the model and controls.
Fault code tables differ slightly between Greenstar generations and controls, so always check the code against the table in your own user manual. If you no longer have it, the model name is on the front of the boiler or under the front flap, and Worcester’s technical support can help identify it.
Is CE 207 dangerous?
Low pressure on its own is not a gas safety risk. The boiler has stopped precisely because it cannot run safely with too little water. The risk is mostly to comfort in winter, and to the boiler if the underlying leak is allowed to continue. If you see water dripping from the boiler itself, or anything other than a clean water leak, switch the boiler off and call an engineer.
Worcester bosch low pressure error: first checks
- Read the gauge with the heating off and the system cold. Pressure rises when the water is hot, so a cold reading is the one that matters.
- Compare with your manual. Most sealed domestic systems are filled to around 1 to 1.5 bar cold, but your manual or installer’s label is the authority for your system.
- Think about what has happened recently. Have you bled radiators, had a radiator removed for decorating, or had plumbing work? Any of these can lower the pressure once and explain a single CE 207.
- Look for obvious water. Check under the boiler, around radiator valves, towel rails and any exposed pipework.
- Check the pressure relief pipe outside. This is a small copper pipe that runs from the boiler through the wall and often turns down towards the ground. If it is dripping or there are water marks beneath it, the boiler is dumping water. See our guide to a pressure relief valve dripping outside.
How to top up pressure and clear CE 207
Topping up is a user-level task on most Greenstar boilers, and Worcester’s user manuals describe the method for each model. The filling arrangement varies: some boilers have an integral filling link under the boiler, often operated with a key or a lever, while others have an external braided filling loop between two taps on the pipework.
The general process is:
- Turn off the boiler and let the system cool.
- Locate the filling loop or filling link. Your manual shows where it is on your model.
- Open the filling valve or valves slowly and watch the pressure gauge rise.
- Close the valve or valves firmly when you reach the recommended cold pressure. Do not overfill.
- If you have an external filling loop that is designed to be disconnected, follow the manual on whether to remove it.
- Switch the boiler back on and reset it if the code does not clear on its own.
Our step-by-step guide on how to repressurise a combi boiler covers the different filling loop types with photos of what to look for. If you overfill, bleeding a radiator can bring the pressure down. If the pressure is still too high, see our article on boiler pressure that is too high.
CE 207 keeps coming back: what it usually means
A sealed heating system should hold its pressure for months. If you are topping up every few days or weeks, water is leaving the system. These are the common causes.
| Cause | Signs | Who fixes it |
|---|---|---|
| Leak on a radiator valve, pipe joint or towel rail | Damp carpet, stains, green or white crust on fittings | Plumber or heating engineer |
| Hidden leak under floors or in walls | No visible water, but pressure falls steadily; damp patches | Engineer with leak detection |
| Pressure relief valve letting by | Drips or staining under the relief pipe outside | Gas Safe engineer (boiler component) |
| Expansion vessel lost its air charge | Pressure swings high when hot, low when cold; relief valve may discharge | Gas Safe engineer |
| Internal leak in the boiler | Water inside the casing or dripping from the boiler | Gas Safe engineer |
| Auto air vent leaking | Small amounts of water near the pump or top of the boiler | Gas Safe engineer |
The expansion vessel and relief valve connection
The expansion vessel is a pressurised tank inside or next to the boiler that absorbs the extra volume when water heats up. If it loses its air charge, the pressure climbs too high as the system heats, the pressure relief valve opens to protect the boiler and releases water outside, and when the system cools the pressure drops low enough to trigger CE 207. Topping up just restarts the cycle. An engineer can check and recharge the vessel, or replace it, and then check whether the relief valve needs replacing too.
For a wider look at pressure loss without visible water, read our guide to a boiler losing pressure with no visible leak. In cold snaps, pressure can also drop slightly as water contracts, which our article on boiler pressure dropping in cold weather explains.
What you should not do
- Do not keep topping up and resetting week after week. Constantly adding fresh water brings in oxygen and dilutes inhibitor, which speeds up corrosion and sludge.
- Do not open the boiler casing to look for leaks or adjust the expansion vessel. Internal work on a gas boiler must only be done by a Gas Safe registered engineer.
- Do not cap or block the pressure relief pipe outside, even if it is dripping. It is a safety device.
- Do not leave the filling loop open, as mains pressure can push the system too high.
Vaillant’s general boiler guidance makes the same distinction that applies to any brand: topping up pressure is a minor fix, but low pressure caused by a leak, or high pressure that bleeding does not solve, needs an engineer, and needing regular resets is not normal.
Related Worcester codes and when to call an engineer
If your Greenstar shows a different code after you top up, it may be a separate fault. For example, EA 227 is an ignition-related code, covered in our guide to the Worcester Bosch EA 227 error. Call a Gas Safe engineer if:
- CE 207 returns within a few weeks of topping up.
- The pressure relief pipe outside drips or has discharged.
- The pressure climbs well above normal when the heating is running.
- You see water inside or under the boiler.
- The boiler will not clear the code even with correct pressure.
Book a Worcester Bosch pressure fault repair
If CE 207 keeps returning on your Greenstar, our Gas Safe registered engineers can trace the leak, test the expansion vessel and pressure relief valve, and get the system holding pressure again. We cover Stoke-on-Trent, Newcastle-under-Lyme, Kidsgrove, Stone and the surrounding area. See our boiler repair service or contact Gasmaster to book an engineer.
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Frequently asked questions
What pressure should my Worcester Bosch boiler be at?
Check your user manual or the label left by your installer, as the correct figure depends on your system. Most sealed domestic systems are filled to around 1 to 1.5 bar when cold. Pressure rises when the heating runs, so always check and top up with the boiler off and the radiators cool.
Can I reset a Worcester boiler showing CE 207 without topping up?
Not usefully. The boiler is blocking operation because the pressure sensor is reading too low. Resetting without restoring pressure will simply bring the code back. Top up to the correct cold pressure first, then reset if the code does not clear. If pressure is already correct and the code stays, the sensor or wiring may be at fault.
Why does my Worcester lose pressure but I cannot find a leak?
The most common hidden causes are the pressure relief valve discharging outside, an expansion vessel that has lost its charge, a leak under floorboards or inside the boiler, or a weeping auto air vent. Check the relief pipe outside first. If it is dry and you still cannot find water, ask a Gas Safe engineer to test the vessel and look for internal leaks.
Does a CE 207 error mean I need a new boiler?
Very rarely. Low pressure faults are usually caused by fixable issues such as a leaking valve, a worn pressure relief valve or an expansion vessel needing recharging. On an older boiler with several other faults, an engineer may discuss repair against replacement, but CE 207 alone is normally a repair job.
How often is it normal to top up boiler pressure?
A healthy sealed system should hold its pressure for many months. Needing to top up once after bleeding radiators is normal. Needing to top up every few days or weeks is not, and it means water is escaping somewhere. Get it investigated before corrosion or a hidden leak causes bigger damage.
Related services
Abdul runs Gasmaster Plumbing & Heating and has worked on boilers, heating and gas appliances across Stoke-on-Trent since 2005. He is Gas Safe registered (reg. 220932), and these articles come from his day to day work in homes and businesses across Staffordshire, Cheshire and Derbyshire.
