Baxi E119 Fault Code: Low Water Pressure
The E119 fault code indicates that your boiler's system pressure has dropped below 0.5 bar, which is too low for safe and efficient operation. Baxi boilers are designed to shut themselves down automatically when this happens, preventing damage to internal components such as the pump and heat exchanger. Until the pressure is restored to the correct level, the boiler will remain locked out and produce no heating or hot water.
General guidance only — not a substitute for professional advice. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
What does the Baxi E119 fault code mean?
The E119 fault code indicates that your boiler's system pressure has dropped below 0.5 bar, which is too low for safe and efficient operation. Baxi boilers are designed to shut themselves down automatically when this happens, preventing damage to internal components such as the pump and heat exchanger. Until the pressure is restored to the correct level, the boiler will remain locked out and produce no heating or hot water.
Common causes
- Pressure lost after bleeding radiators Common
Releasing trapped air from radiators is the most common reason for a sudden pressure drop. Every time air is bled, a small amount of water is displaced and lost from the sealed system, which can push pressure below the 0.5 bar threshold and trigger E119.
- Slow leak somewhere in the system Common
A dripping radiator valve, a weeping joint in the pipework, or a small leak at the boiler itself can cause pressure to fall gradually over days or weeks. If you find yourself repressurising more than once every few months, a leak is the most likely explanation and a Gas Safe engineer should be called to locate it.
- Natural pressure loss over time Common
Sealed heating systems do lose tiny amounts of pressure through normal use — micro-bubbles escaping through joints, minor thermal cycling, and so on. A small top-up once or twice a year is entirely normal and not necessarily a sign of a fault.
- Faulty or weeping pressure relief valve (PRV) Sometimes
The PRV is a safety device that releases water if pressure climbs dangerously high. If the valve seat has worn or the valve has opened too many times, it may weep continuously, allowing water to escape slowly down the condensate or overflow pipe outside. You may notice a damp patch or dripping near the boiler's external discharge pipe.
- Waterlogged or under-charged expansion vessel Sometimes
The expansion vessel absorbs the increased volume of water as it heats up. If its internal membrane has failed or the pre-charge air pressure has dropped, the vessel can no longer do its job properly, causing pressure to fluctuate and drop — or to repeatedly spike and trigger the PRV to release water.
- Frozen condensate pipe (winter months only) Rare
In very cold weather, the plastic condensate pipe that runs outside the property can freeze solid. This prevents the boiler from condensing correctly and can contribute to a pressure-related lockout alongside other fault codes. If E119 appears during a cold snap, check the condensate pipe for blockage.
- Internal boiler leak — heat exchanger or pump seal Rare
Occasionally, a crack or pinhole in the primary heat exchanger, or a failing pump seal, allows water to leak internally. This is less common but more serious, and will cause persistent pressure loss that cannot be resolved by simply topping up the system.
How to fix it
- Check the pressure gauge reading DIY safe
Look at the pressure gauge on the front of your boiler — on most Baxi models it is either a dial gauge or a digital display. A healthy cold-system pressure sits between 1.0 and 1.5 bar. If the needle or reading is below 1.0 bar (and especially if it is near zero), low pressure is confirmed as the cause of E119.
- Top up the system pressure using the filling loop DIY safe
Switch the boiler off and allow it to cool for at least 20–30 minutes. Locate the filling loop — usually a short braided metal hose with one or two valves beneath the boiler. Open the valve(s) slowly and watch the pressure gauge rise. Stop when it reaches 1.2–1.5 bar. Close the valve(s) fully. Some Baxi models have a built-in Easy-Fill lever instead; press or pull this until the correct pressure is reached, then release it. Never overfill above 1.5 bar when cold.
- Thaw a frozen condensate pipe if applicable DIY safe
If the fault has appeared during freezing weather, inspect the white plastic condensate pipe that exits the boiler and runs outside (often to a drain or down an external wall). If it feels solid or is visibly iced over, warm it gently using a hot water bottle, a microwaveable heat pack, or warm (not boiling) water poured carefully along its length. Boiling water can crack the pipe or fittings.
- Reset the boiler DIY safe
Once pressure is at the correct level, reset the boiler by turning the selector dial to the R (Reset) position. Hold it there for at least five seconds, then release. The E119 code should clear and the boiler should restart normally. If it does not clear after two or three attempts, do not continue resetting — move on to the next step.
- Monitor the pressure over the next 24–48 hours DIY safe
Keep an eye on the gauge over the following two days. If pressure holds steady, the issue was simply low pressure from bleeding radiators or gradual natural loss. If pressure drops again quickly — within hours or within a day — you almost certainly have a leak somewhere in the system and should not keep topping it up. Repeatedly masking a leak with top-ups can cause corrosion and damage over time.
- Inspect radiators, visible pipework and the boiler casing for signs of leaks DIY safe
Walk around the property and look at all accessible radiator valves, pipe joints and connections for damp patches, rust staining, or white limescale deposits (a tell-tale sign of dried water drips). Check the floor beneath the boiler and around the condensate or discharge pipe outside. If you spot anything suspicious, note the location ready to tell the engineer.
- Call a Gas Safe registered engineer Gas Safe engineer
If pressure keeps dropping, you cannot identify the source of a leak, or the boiler fails to stay lit after repressurising, you need a Gas Safe registered engineer. They can pressure-test the system to locate hidden leaks, inspect and replace a faulty PRV, re-charge or replace the expansion vessel, and investigate any internal boiler components such as the heat exchanger or pump seals. Do not attempt to open the boiler casing or work on any gas components yourself.
Parts you may need
- Expansion vessel (12 litre, combi boiler) · from £45
- Expansion vessel membrane / diaphragm · from £18
- Pressure relief valve (3 bar PRV) · from £22
- Filling loop assembly (Baxi compatible) · from £15
- Radiator bleed valve replacement kit · from £8
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £120–£350, depending on the underlying cause.
Frequently asked questions
Can I repressurise my Baxi boiler myself to fix E119?
Yes — topping up the system pressure via the filling loop or Easy-Fill lever is a straightforward task that most homeowners can do safely. Switch the boiler off, let it cool, then open the filling loop valves until the gauge reads 1.2–1.5 bar. Close the valves and reset the boiler. The whole process takes around five minutes. However, if the pressure drops again within a day or two, stop topping it up and call a Gas Safe engineer — you likely have a leak that needs finding and fixing properly.
Why does my Baxi boiler keep losing pressure and showing E119 repeatedly?
If E119 keeps coming back after you top up the system, there is almost certainly a leak somewhere. Common culprits include a weeping pressure relief valve (look for a damp or dripping discharge pipe outside), a leaking radiator valve, a joint in the pipework, or — less commonly — an internal boiler component such as the heat exchanger or pump seal. A failing expansion vessel can also cause repeated pressure loss. A Gas Safe engineer can pressure-test the whole system to find the source. Do not keep repressurising indefinitely, as this can accelerate corrosion and introduce excess oxygen into the system.
How much does it cost to fix E119 on a Baxi boiler?
If you repressurise the system yourself, the fix costs nothing. If an engineer is needed to repressurise and check the system, expect a call-out fee of roughly £60–£100. Repairing a leak in the pipework or replacing a pressure relief valve typically costs £120–£350 including parts and labour. Replacing an expansion vessel usually falls within the same range. In rare cases where an internal heat exchanger leak is found, costs can be considerably higher — a Gas Safe engineer will advise once the fault is diagnosed.
Is E119 dangerous — should I be worried?
E119 itself is not a gas safety emergency. Low pressure causes the boiler to shut down as a protective measure, so the boiler simply stops working rather than posing an immediate hazard. However, you should not ignore it, as running a heating system with a persistent leak can cause long-term damage to pipework and radiators through corrosion. If the E119 code appears alongside any smell of gas, you should turn off the gas supply at the meter, open windows, leave the property, and call the National Gas Emergency Service on 0800 111 999 immediately.