Worcester Bosch CE 207 fault codewhat it means and how to fix it
System water pressure has dropped too low for the boiler to run safely. Topping the system back up to 1.2 bar usually clears it in five minutes.
Take care
What is the gauge doing?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
It is low and this is the first time in a year or more
Normal gradual loss. Top up to 1.2 bar, reset, and get on with your day.
You have topped it up more than twice in six months
That is a leak. Continually refilling brings oxygenated water into the system, which is what produces the black sludge that ruins radiators and pumps.
Book a leak trace rather than topping up again.
It drops to zero within hours of filling
Loss at that rate is a significant leak, and there is a real risk of water damage somewhere you have not looked yet.
Do not keep refilling. Turn the boiler off and get someone out — check under floors, in the airing cupboard, and around the boiler itself.
What CE 207 means
CE 207 is Worcester Bosch signalling low system pressure. The boiler measures the pressure of the sealed heating circuit and stops firing when it falls too low — Worcester's user guide tells you to re-charge as soon as the gauge reads under 1 bar — because running a heat exchanger without enough water in it destroys it very quickly.
On the Compact ranges that publish this code it is a blocking code, not a lockout: the boiler restarts on its own once the pressure is back. The lockout is a protection, not a fault in itself. What matters is why the pressure fell. A sealed system does not consume water, so a falling gauge means water is leaving — through a weeping valve, a hidden pipe joint, a failed expansion vessel, or a pressure relief valve that is passing. Topping up is the immediate fix; finding the loss is the real one.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Slow leak somewhere in the system | Radiator valve glands and compression joints under floors are the usual places. Slow enough to evaporate before it stains. | Common |
| Radiators recently bled | Bleeding removes water from a sealed system. Several radiators drops the gauge noticeably. | Common |
| Failed expansion vessel | A perished bladder means pressure spikes when the system heats and vents out through the safety valve, losing a little each cycle. | Occasional |
| Passing pressure relief valve | Look for the copper discharge pipe outside the wall. Dripping or limescale staining confirms it. | Occasional |
What to try yourself
Check the pressure gauge with the boiler cold. Below 1.0 bar confirms the fault; between 1.0 and 1.5 is normal.
Locate the filling loop. On most Greenstar installations it is a braided hose under the boiler; on Greenstar i models it is often a keyed internal filling link at the base of the appliance.
Open the valves slowly and watch the gauge. Close them at 1.2 bar.
Never exceed 2.5 bar cold. Overfilling forces water out of the safety valve and you will end up back at low pressure with a wet patch outside.Close the loop fully and hold the reset button for five seconds.
Note the date. If you are doing this more than twice a year, the system has a leak that needs finding.
Get a Gas Safe registered engineer to look at your Worcester Bosch CE 207
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What it costs to fix
Typical repair cost
£0–£450
Time on site
10 minutes
Free if it just needs topping up. Leak trace £90–£160. Expansion vessel £150–£280. Lifting floors to reach a pipe leak can reach £450 or more.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Expansion vessel (8 litre, sealed system)
EV-8L£35–£85Plumbing merchant
Price checked 28 September 2026
Pressure relief valve, 3 bar
PRV-3B£18–£42Plumbing merchant
Price checked 28 September 2026
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Related Worcester Bosch fault codes
- H07Get it checkedA maintenance warning, not a lockout. The boiler is still running but water pressure has fallen far enough to limit how well it heats.Related: water pressure
- 1065Get it checkedThe system pressure sensor is faulty or not connected. The boiler cannot read its own water pressure, so it stops rather than guess. Worcester check the plug, the harness, the voltage, then the sensor.Related: water pressure
- 2970Get it checkedThe heating system's pressure has dropped too quickly too often. On an 8000 with the intelligent filling loop this usually follows venting after an automatic fill; otherwise it is a leak that needs finding.Related: water pressure
- EA 227Stop — call an engineerThe boiler tried to light and never detected a flame, so it has shut the gas off and locked out. This is the most common Worcester fault code.Related: same brand
- E9 219Stop — call an engineerThe boiler has overheated and the safety thermostat has tripped. Water is not carrying heat away from the exchanger, and it should not be run until that is fixed.Related: same brand
- C6 224Get it checkedThe fan is not reaching the speed the boiler asked for, so combustion cannot be confirmed as safe and the burner has been prevented from firing.Related: same brand
Own a Worcester Bosch boiler? Save it and its codes come first next time.
Related guides
Common questions about Worcester Bosch CE 207
What pressure should a Worcester Bosch boiler run at?
Between 1.0 and 1.5 bar cold, with 1.2 bar the usual target. It rises when the heating is on, and up to about 2.0 bar hot is normal. Always set it with the system cold.
Where is the filling loop on a Greenstar?
On most installations it is a braided silver hose with a valve at each end, below the boiler. On many Greenstar i models it is built in: a plastic key at the base slots into the filling link and turns to open it. If you cannot find either, do not force anything — ask an engineer to show you once and you will know for good.
Why does the pressure fall every time it gets cold?
Cold weather means more running hours, so a slow leak loses more, and it is when people bleed radiators. If the drop only ever happens in winter, there is usually a small leak that goes unnoticed the rest of the year.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Manufacturer support portal
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.