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 refuses to fire below roughly 0.5 bar, because running a heat exchanger without enough water in it destroys it very quickly. 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
Gas Safe Register engineers only. No obligation.
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 August 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 5 August 2026
Pressure relief valve, 3 bar
PRV-3B£18–£42Plumbing merchant
Price checked 5 August 2026
What other owners found
Nobody has shared what worked for them on this code yet. If you have had it, you would be the first — and it genuinely helps the next person.
Related Worcester Bosch fault codes
- F.22Get it checkedThe boiler has shut down because there is not enough water in the system. Pressure has dropped below roughly 0.5 bar and it will not fire until you top it up.Related: water pressure
- F.75Get it checkedThe boiler cannot detect a rise in pressure when the pump starts, so it has locked out. Usually a failed pressure sensor or a pump that is not moving water.Related: water pressure
- F1Get it checkedSystem pressure has dropped below the minimum the boiler will run at. Topping it back up to 1.2 bar usually clears it straight away.Related: water pressure
- E10Usually simple to fixSystem water pressure has fallen too low for the appliance to fire. Top the system back up to 1.2 bar and it will restart.Related: water pressure
- 108Usually simple to fixThe heating circuit does not contain enough water to run safely. Refill through the filling loop to about 1.2 bar and the code clears.Related: water pressure
- E119Get it checkedSystem pressure has fallen below the level the boiler will operate at. Refilling to 1.2 bar and resetting usually clears it in a few minutes.Related: water pressure
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.
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
- Interviews with working engineers
Checked by Technical reviewer (Gas Safe registration to be displayed on appointment) on 5 August 2026.