What the E119 code means
On most current Baxi combis, E119 means the water pressure is too low, or in Baxi's terms, the water pressure switch is not made. Inside the boiler there is a pressure switch or sensor that must detect enough pressure before the boiler is allowed to light. When the pressure falls too far, the switch stays open and the boiler shows E119 instead of running.
The heating system is a sealed circuit of water. It needs pressure to push water around the radiators and to protect the pump and heat exchanger from overheating. Stopping the boiler when pressure is low is a deliberate safety step.
This is one of the Baxi faults that homeowners can usually clear themselves. What matters is working out whether the drop was a one-off or a sign of an ongoing problem.
Common causes of E119
| Cause | What you might notice | Who fixes it |
|---|---|---|
| Radiators recently bled | Pressure fell after bleeding | You (top up) |
| Leak on pipework or radiator valves | Drips, damp floorboards, staining or rust | You to find it, a plumber to repair |
| Pressure relief valve discharging | Water dripping from the copper pipe outside | Gas Safe engineer |
| Expansion vessel lost its charge | Pressure climbs high when hot and falls when cold | Gas Safe engineer |
| Faulty pressure switch or sensor | Gauge looks normal but E119 remains | Gas Safe engineer |
| Leak inside the boiler | Water under the boiler or on the casing | Gas Safe engineer |
How the expansion vessel affects pressure
As water heats up it expands. The expansion vessel, a small tank inside the boiler on most Baxi combis, takes up that extra volume. If it loses its air charge, the pressure rises too far when the heating runs and the pressure relief valve lets water out. Once the system cools, the pressure is lower than it was. Repeated over time, this leads to E119.
Pressure drops after other work
If E119 appeared soon after a radiator was replaced, a valve was changed or the system was drained for any reason, the system may simply not have been refilled to the right pressure. Air trapped during the work can also escape through the radiators over the following days, which lowers the pressure further. In this case, bleeding the radiators and topping up once or twice is often all that is needed. If the drop continues after a week or so, treat it as a possible leak.
Safe checks you can do yourself
These steps are safe for homeowners. Do not remove the boiler casing.
- Check the gauge. With the heating off and cool, look at the pressure gauge or the reading on the display. Below 1 bar means it needs topping up.
- Find the filling loop. Some Baxi models have a built-in filling loop under the boiler, others use a separate braided hose with two valves. Your manual shows which yours has.
- Top up to 1 to 1.5 bar. Open the valves slowly, watch the gauge and close them once the reading reaches 1 to 1.5 bar. Our guide on how to repressurise a boiler walks through it step by step.
- Reset if needed. On many models E119 clears once the pressure is restored. If not, press the reset button as your manual describes, no more than 2 or 3 times.
- Check for leaks. Look around radiators, valves, visible pipes and underneath the boiler.
- Check the relief pipe outside. A short copper pipe usually runs through the wall near the boiler. If it drips, water is being released from the system.
- Monitor the pressure. Note the gauge reading each day for a week. A steady fall means there is a problem to fix.
Do not overfill the system. If the cold pressure is above 1.5 bar, it may rise too high when hot. Our guide to boiler pressure that is too high explains how to bring it down.
When to call a Gas Safe engineer
Pressure dropping once after bleeding radiators is normal. If you are topping up regularly, or E119 keeps returning, book a Gas Safe registered engineer.
Call straight away if you see water coming from the boiler, if the outside relief pipe is dripping, or if the gauge reads normal but the code will not clear. The last sign often means the pressure switch or sensor has failed. The expansion vessel, relief valve and pressure switch are all inside the boiler, so they must only be checked by an engineer.
If you find a leak on a radiator or pipework away from the boiler, a plumber can normally fix it. For leaks at the boiler itself, see our guide to a boiler leaking water.
Typical repair costs in the UK
These are typical ranges, not quotes. Prices depend on your area, access and the parts needed.
| 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 switch or sensor replacement | Typically £100 to £200 |
| Leak repair on pipework or a radiator valve | Varies with access, quoted after inspection |
How to stop E119 coming back
- Check the gauge once a month, and before the start of winter.
- Top up after bleeding radiators, as bleeding always lets out some pressure.
- Repair small leaks early. A slow drip can empty enough water to trigger E119 within weeks.
- Have the boiler serviced every year. The engineer can check the expansion vessel and relief valve. See our guide to boiler service costs.
Mark the correct cold pressure on the gauge glass with a small sticker or a dab of marker. It makes a drop easy to spot at a glance.