What the CE 207 code means
On most Greenstar models, CE 207 means the water pressure in the central heating system is too low. The boiler has a pressure sensor that constantly measures this. If the reading drops below a safe minimum, usually well under 1 bar, the boiler stops working to protect itself and shows CE 207.
Your heating system is a sealed loop of water, and it needs a certain amount of pressure to circulate properly and keep the boiler's internal parts safe. Without enough pressure the pump and heat exchanger can overheat or be damaged, so the shutdown is deliberate.
The good news is that this is one of the few boiler faults most homeowners can put right themselves. The important part is finding out why the pressure dropped, so it does not keep happening.
Common causes of CE 207
Pressure in a sealed system should stay fairly steady. If it has fallen, something has let water out or the system cannot hold its pressure.
| Cause | What you might notice | Who fixes it |
|---|---|---|
| Radiators recently bled | Pressure dropped soon after bleeding | You (top up) |
| Small leak on pipework or a radiator valve | Damp patches, drips, staining or rust marks | You to spot it, a plumber to repair |
| Pressure relief valve letting water out | Drips from the copper pipe outside the wall | Gas Safe engineer |
| Expansion vessel lost its charge | Pressure rises high when hot, then falls when cold | Gas Safe engineer |
| Faulty pressure sensor | Gauge reads normal but code still shows | Gas Safe engineer |
| Leak inside the boiler | Water under the boiler | Gas Safe engineer |
A note on the expansion vessel
The expansion vessel is a tank inside or next to the boiler that absorbs the extra volume of water as it heats up. If it loses its air charge, pressure shoots up when the heating is on. The pressure relief valve then lets water out, and when the system cools the pressure is lower than before. Over days or weeks this cycle leads to CE 207.
Pressure drops after other work
If CE 207 appeared shortly after a radiator was changed or the system was drained, it may not have been refilled to the right level. Air trapped during the work can also escape over the following days, lowering the pressure further. Bleeding the radiators and topping up once or twice usually sorts this out.
Safe checks you can do yourself
These steps are safe for a homeowner. Do not remove the boiler casing.
- Read the pressure gauge. With the heating off and cold, check the gauge or the display. If it is below 1 bar, the pressure needs topping up.
- Find your filling link or loop. Many Greenstar models have a built-in filling link under the boiler, while others use a separate braided filling loop. Your manual shows which you have.
- Top up to 1 to 1.5 bar. Open the filling link or loop slowly, watch the gauge rise, and close it again once you reach 1 to 1.5 bar. Our guide on how to repressurise a boiler covers this in detail.
- Reset the boiler if the code does not clear on its own. Press or hold the reset button as described in your manual, no more than 2 or 3 times.
- Look for leaks. Check around radiators, radiator valves, exposed pipes and under the boiler for damp, drips or staining.
- Check the pressure relief pipe outside. This is usually a short copper pipe coming through the wall near the boiler. If it drips, the relief valve may be letting water out.
- Watch the gauge for a few days. Note the reading each morning. A drop of more than a small amount over a week points to a leak or a fault.
Do not overfill. If you go above 1.5 bar when cold, the pressure can climb too high once the heating warms up. See our guide to boiler pressure that is too high if this happens.
When to call a Gas Safe engineer
A single drop after bleeding radiators is normal. If you need to top up more than once every few weeks, something is wrong and you should book a Gas Safe registered engineer.
Call one straight away if you see water leaking from the boiler itself, if the pressure relief pipe is dripping, or if the gauge reads normal and CE 207 still shows. That last sign often points to a faulty pressure sensor. An engineer can test the sensor, recharge or replace the expansion vessel and check the pressure relief valve, all of which sit inside the boiler.
If you find a leak on pipework or a radiator away from the boiler, a plumber can usually repair it. Our guide to a boiler leaking water explains what to do if the leak is at the boiler.
Typical repair costs in the UK
These are typical ranges and will vary with location, access and parts. They are not quotes.
| Repair | Typical cost |
|---|---|
| Topping up pressure yourself | Free |
| Engineer call-out and diagnosis | Typically £80 to £150 |
| Expansion vessel recharge | Typically £80 to £150 |
| Pressure sensor replacement | Typically £100 to £200 |
| Leak repair on pipework or radiator valve | Varies with access, quoted after inspection |
How to stop CE 207 coming back
- Check the gauge monthly, especially before winter, so you catch a slow drop early.
- Top up after bleeding radiators. Bleeding always releases a little pressure.
- Fix small leaks quickly. Even a slow drip from a radiator valve will pull the pressure down over time.
- Have the boiler serviced every year. The engineer can check the expansion vessel charge and the relief valve. Our guide to boiler service costs explains what is included.
Take a photo of the gauge when the system is cold and working well. It gives you a reference point if you are ever unsure whether the pressure has dropped.