Baxi E119 Fault: Low Water Pressure — Causes & What To Do
The E119 fault on a Baxi boiler means the system water pressure is too low — the water pressure switch hasn't operated, so the boiler has locked out. It's usually a simple repressurise via the filling loop, but if pressure keeps dropping there's a leak or a faulty pressure switch to find.
What does the Baxi E119 fault code mean?
E119 indicates the system water pressure has fallen below the boiler's safe operating level — the water pressure switch hasn't operated. The boiler locks out to protect the pump and heat exchanger from running dry. You'll usually have no heating or hot water.
Why is my Baxi boiler showing E119?
The most common causes, in order of how often we see them:
- • Low system pressure — pressure has simply dropped below the safe level and needs topping up via the filling loop. The most common E119 cause.
- • A leak on the system — if pressure keeps falling after a top-up, water is escaping somewhere: a radiator valve, joint, or hidden pipe under a floor.
- • Faulty water pressure switch — the switch can fail or drift, reporting low pressure even when the system is full.
- • Air in the system — trapped air causes erratic pressure readings and can contribute to low pressure.
Can I reset the E119 fault?
Repressurising the system to around 1.2–1.5 bar via the filling loop and resetting the boiler usually clears E119. If pressure holds, the fix is complete. If it drops again within hours or days, there's a leak or a faulty switch — a reset won't help. Book an engineer.
Can I fix this myself?
Safe homeowner checks
- Check the pressure gauge on the boiler front (healthy is 1.0–1.5 bar)
- Repressurise to 1.2 bar via the filling loop if it's low
- Bleed radiators to release trapped air, then re-check pressure
- Read the fault code and note it down
- Try one boiler reset after repressurising
Engineer required
- Replacing the water pressure switch
- Tracing a hidden leak under floors or in walls
- Inspecting the filling loop, PRV and expansion vessel
- Any internal work inside the boiler casing
- Re-commissioning the boiler after any internal repair
Gas work legally requires a Gas Safe Registered engineer. Tampering with gas appliances is dangerous and unlawful.
Safe checks you can make first
- • Check the pressure gauge — a healthy system sits between 1.0 and 1.5 bar when cold. If it's below 0.5 bar, low pressure is your E119 trigger.
- • Repressurise via the filling loop to around 1.2–1.5 bar, then reset the boiler. If the fault clears and pressure holds, the fix may be complete — but watch for it dropping again.
- • Bleed radiators if they're cold at the top or you hear gurgling — trapped air causes erratic readings. Re-check pressure afterwards, as bleeding lowers it.
- • If pressure keeps dropping after a top-up, there's a leak or a faulty pressure switch — book a Gas Safe engineer to find the source.
Need this fault diagnosed? Book a Gas Safe engineer.
What should you NOT attempt yourself?
The water pressure switch sits inside the boiler casing. Replacing it, or any work inside the casing, is gas/electrical work that must be done by a Gas Safe Registered engineer. If there's no visible leak and pressure still falls, the leak may be under a floor — that needs professional leak detection, not DIY.
What will a Gas Safe engineer check?
- • Confirm system pressure on the gauge and with a calibrated reading.
- • Test the water pressure switch's operation against actual system pressure.
- • Check for leaks — visual inspection plus leak detection if the source is hidden.
- • Inspect the filling loop, pressure relief valve and expansion vessel.
- • Replace the pressure switch if faulty, then re-commission the system.
How Urban Suburban can help
Our Gas Safe Registered (594547) engineers repair every Baxi model — Platinum, EcoBlue, Duo-tec, 600, 400, 800 and MainEco — across Surrey, Berkshire, Buckinghamshire and West London, and carry common sensors, fans and ignition parts on the van. Most Baxi fault-code repairs are completed in a single visit, with any part quoted and agreed before fitting.
Related Baxi fault codes
Frequently asked questions
What does the Baxi E119 fault code mean?
E119 means the system water pressure is too low for the boiler to run safely — the water pressure switch hasn't operated, so the boiler has locked out. You'll usually have no heating or hot water. The most common cause is simply low pressure that needs topping up via the filling loop.
How do I repressurise my Baxi boiler?
Use the filling loop to let mains water into the system until the pressure gauge reads around 1.2–1.5 bar, then close the filling loop and reset the boiler. Our 'How to Top Up Boiler Pressure' guide walks through it step by step.
Why does my Baxi boiler pressure keep dropping?
If pressure falls again soon after topping up, water is leaving the system — usually through a leak at a radiator valve or joint, a hidden pipe leak, a passing pressure relief valve, or a failed expansion vessel. A Gas Safe engineer can find and fix the source.
How much does it cost to fix a Baxi E119 fault?
If it's just low pressure, repressurising is free and takes a minute. If a pressure switch or a leak needs fixing, labour typically runs £90–£220 plus the £150 call-out (which includes the first hour), with any part quoted and agreed before fitting.
Technical content & review
Technical content by URBAN SUBURBAN GAS
Gas Safe Registration: 594547 · NVQ Qualified engineers
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