Worcester Bosch H07 status codewhat it means
A maintenance warning, not a lockout. The boiler is still running but water pressure has fallen far enough to limit how well it heats.
Take care
How often has this message appeared?
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.
This is the first time you have seen it
Routine. The system has slowly given up a little water and is telling you before it becomes a problem.
Top up to 1.5 bar and carry on.
It keeps coming back every few weeks
That rate of loss is not normal seepage. Something is passing water, and every refill brings fresh oxygenated water in that corrodes the system from the inside.
Have the cause traced rather than topping up again.
There is a copper pipe dripping outside the wall
That is the safety valve discharge. The boiler is pushing water out because the expansion vessel can no longer absorb the increase when the system heats.
Ask an engineer to test and recharge or replace the vessel.
What H07 means
H07 belongs to the H family, which Worcester uses for maintenance messages rather than shutdowns. The appliance keeps working while the message is on screen, but it holds back output on both radiators and hot water because there is not enough water in the sealed circuit to move heat away properly. That distinction is the whole point of the code.
A lockout stops everything and demands attention; H07 lets you carry on with a degraded service and quietly warns you that the pressure is heading somewhere it should not go. Left alone it usually becomes a hard low-pressure lockout within days or weeks. Treat it as the early warning it is, top the system back up, and note the date so you can tell whether the loss is gradual or accelerating.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Gradual pressure loss over months | Every sealed system loses a little through valve glands and joints. Most need a small top-up once a year or so. | Common |
| Radiators bled recently | Letting air out also lets water out. Doing a whole houseful in one afternoon can drop the gauge below the warning threshold. | Common |
| Expansion vessel losing its charge | A vessel that no longer holds pressure lets the system vent through the safety valve each time it heats up. | Occasional |
| Leak developing somewhere in the pipework | If the warning returns within weeks of a top-up, water is escaping faster than normal seepage explains. | Occasional |
What to try yourself
Read the gauge with the heating off and the boiler cold. H07 normally appears somewhere under 0.8 bar.
Find the filling arrangement — a braided hose beneath the appliance on most installations, or a keyed internal link on many Greenstar i units.
Bring the needle up to 1.5 bar, then shut both ends of the loop firmly.
Do not chase a higher figure. Above about 2.5 bar cold the safety valve will dump the excess outside and you will be back where you started.The message should clear on its own once pressure is restored. If it persists, hold reset for five seconds.
Write the date somewhere. Two top-ups inside six months is a leak, not maintenance.
Get a Gas Safe registered engineer to look at your Worcester Bosch H07
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–£280
Time on site
10 minutes
Free to top up yourself. Leak trace £90–£160. Expansion vessel £150–£280 fitted.
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
- CE 207Get it checkedSystem 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.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 H07
Is H07 the same as CE 207?
No, and the difference matters. H07 is a maintenance message that leaves the boiler running at reduced output. CE 207 is a lockout — the appliance refuses to fire at all. H07 very often turns into CE 207 if you ignore it.
Can I keep using the heating while H07 shows?
Yes, for a short period. The boiler has decided it is safe to run but not safe to run flat out. You will probably notice radiators taking longer to warm and hot water being less consistent. It is not a reason to switch anything off, but it is a reason to deal with it this week rather than next month.
Why do H codes exist at all?
They are Worcester flagging something an engineer should look at without punishing you with a cold house in the meantime. Nothing about an H code is an emergency, and nothing about it should be left indefinitely either.
What does it cost?
Nothing if you top it up yourself. A leak trace runs £90 to £160. An expansion vessel replacement is £150 to £280 depending on how awkward the boiler is to strip.
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
- Manufacturer documentation checked — this code is not published in it, and we say so on the page
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.