Baxi E119 Fault Code: Low System Pressure

What the Baxi E119 fault code means

On a Baxi boiler, the E119 fault code indicates low water (system) pressure. Your central heating is a sealed, pressurised circuit, and the boiler constantly monitors that pressure using a sensor. When the reading falls below the minimum the boiler needs to run safely, it locks out and displays E119 rather than continuing to fire. It is one of the most common Baxi fault codes — and, reassuringly, one of the few that you can often resolve yourself.

You will usually find that the heating and hot water stop working, the pressure gauge on the front of the boiler is reading below 1 bar, and the display is showing E119. The good news is that low pressure is a symptom rather than damage in itself, so topping the system back up will normally clear the code.

Why does the pressure drop?

A small, gradual loss of pressure over many months is normal as tiny amounts of air work out of the system. A noticeable or repeated drop usually points to one of the following:

• Recently bled radiators — releasing trapped air lowers the system pressure, so the gauge often drops after a bleed.
• A small leak somewhere in the pipework, on a radiator valve, or at a joint.
• A failing expansion vessel, which can no longer absorb the expansion of heated water.
• A weeping or faulty pressure relief valve (PRV), which may be letting water escape through the external discharge pipe.

If you have to repressurise once and the boiler then behaves for months, there is little to worry about. If the pressure keeps dropping every few days, something needs investigating by an engineer.

How to repressurise a Baxi boiler safely

Topping up the pressure via the filling loop is a homeowner-safe job — it involves the water side of the system only, not the gas. Work slowly and keep an eye on the gauge.

1. Turn the boiler off and let it cool. It is easier and safer to set the pressure on a cold system.
2. Locate the filling loop. This is usually a silver braided hose with a valve (or two) underneath the boiler, connecting the cold mains to the heating pipework. Some Baxi models have a built-in keyed filling valve instead.
3. Open the valve(s) slowly. You should hear water flowing into the system. Watch the pressure gauge begin to climb.
4. Stop at 1 to 1.5 bar. Close the valve(s) firmly as soon as the needle reaches this range. Do not let it climb past 1.5 bar cold.
5. Reset the boiler. Most Baxi models clear the lockout automatically once pressure is restored; if not, use the reset button on the front panel once. The E119 code should disappear and the boiler should fire up.
6. Return the filling loop to its normal state — close it fully, and on some models disconnect the hose as the manufacturer advises.

When to call a Gas Safe registered engineer

Repressurising once is fine. But you should book a Gas Safe registered engineer if any of the following apply:

• The pressure keeps dropping and you are repressurising every few days — this points to a leak, a faulty expansion vessel or a failing PRV.
• You can see water dripping from the boiler, from pipe joints, or from the external discharge pipe outside the wall.
• The E119 code returns immediately or the boiler will not refill at all.
• You are not confident locating or operating the filling loop.

Diagnosing and replacing an expansion vessel, pressure relief valve or a hidden leak is not a DIY job — it involves the sealed pressurised circuit and the boiler's internals, so it must be done by a registered engineer. You can check any engineer's credentials on the Gas Safe Register. If you ever smell gas, leave the property and call the national gas emergency line on 0800 111 999.

Where boiler cover comes in

A persistent E119 caused by a faulty expansion vessel or a leaking PRV can mean a callout charge plus parts. A boiler cover or central heating policy can spread that cost into a fixed monthly payment, with parts and labour included, and an annual service that often catches a tired expansion vessel before it fails. If you are weighing it up, our guide on whether boiler cover is worth it walks through the maths, and what boiler cover actually includes explains the typical exclusions to watch for.

For the specifics of low pressure itself — and how to stop it recurring — see our companion guide on what to do when your boiler pressure is too low.