E119 on a Baxi or Potterton boiler is a low water pressure fault: the water pressure switch has not seen enough pressure in the sealed circuit, which the manuals put at below 0.5 bar, so the boiler stops. Topping up through the filling loop normally clears it. If the pressure falls again within days, something is losing water.
A Baxi E119 usually turns up with the heating dead and the radiators stone cold. As fault codes go it is a kind one: the first step takes a few minutes and you can do it yourself. What tells you more is the gauge over the next fortnight, because that separates a system that simply needed topping up from one quietly losing water into a floor.
On this page
- What the Baxi E119 fault code means
- How to clear E119: repressurising the system
- The test that tells you whether you have a leak
- Why E119 keeps coming back
- Who to call, and when it is not a leak job
- What a hidden heating leak actually looks like
- Buried heating pipes in Cornwall and Devon homes
- Frequently asked questions
What the Baxi E119 fault code means
Your central heating runs as a sealed circuit. The same water goes round the radiators for years, and because nothing tops it up automatically, the boiler watches that circuit with a water pressure switch. Baxi and Potterton fault tables word E119 as that switch not operating, and their manuals say it shows when the primary water pressure is less than 0.5 bar. In practice the circuit is low on water, although a faulty switch or its wiring can produce the same code.
Some Baxi and Potterton ranges use E118 for the same condition instead. Baxi’s own error code list gives E118 as water pressure low, below 0.5 bar, and the response is identical either way.
Normal cold pressure on these boilers is typically around 1 to 1.5 bar, though the figure varies by model, so check your own manual. Most gauges have the safe band marked on the dial, and that marking is what to work to.
How to clear E119: repressurising the system
Bringing the pressure back up is a normal homeowner job; Baxi calls it a simple job you can do yourself. There are two common arrangements: a filling loop, a braided metal hose with a tap at each end, or a Baxi Easy-Fill link, a built-in fitting with a green lever you hold open. On many installations the loop hose is not left connected, and the two taps sit capped under the boiler until you need them.
- Turn the boiler off and let it cool, then note the gauge. Pressure is only meaningful on a cold system.
- With a filling loop, uncap the two taps and connect the braided hose between them, tightening the nuts by hand. Open one tap fully, then the second slowly. With an Easy-Fill link, hold the lever open. You should hear water moving into the system.
- Watch the gauge and stop as soon as it reaches the cold band marked for your model, usually around 1 to 1.5 bar. Do not carry on past it.
- Close both taps fully and take the hose off, or release the Easy-Fill lever. A tap left open keeps feeding mains water into a sealed circuit. Turn the boiler back on. Potterton’s guide says it should run again once the pressure is up; if not, your manual gives the reset for your model.
If you overshoot, bleed a little out of a radiator until the needle drops back. Our guide to increasing boiler pressure covers this in more detail, including what to do if you cannot find the filling loop.
If the Baxi E119 code returns straight away
A code that comes back within minutes of a top-up, with the gauge still in the right band, is a different problem from one that returns a fortnight later. The first can point to a faulty pressure switch or gauge, which is a heating engineer’s job. The second means the water is going somewhere.
The test that tells you whether you have a leak
This is the part most people skip, and it answers the question. Once you have topped up, note the gauge reading and the date, then leave the system alone and check weekly.
If the needle is still where you left it a month later, the system was simply low, most likely after radiators were bled, or the occasional top-up Baxi says all boilers need. There is no leak and nothing needs tracing.
If the pressure falls again within days or weeks, with no water on the floor, no damp patch and no drip from the pipe outside, that is the pattern that matters. Our guide to why a boiler keeps losing pressure covers the diagnosis in more depth.
Why E119 keeps coming back
A sealed system does not consume water. If the pressure keeps dropping, four explanations are worth working through.
Air was bled out and never replaced
Bleeding radiators releases air and pressure falls with it, which is why the advice is always to check the gauge afterwards. If nobody tops the system back up, the boiler can drop into E119 next time the heating fires. Top it up once and it stays put.
The expansion vessel has lost its charge
The expansion vessel absorbs the extra volume water takes up as it heats. When it loses its gas charge, or the diaphragm inside splits, pressure swings high while the heating runs then falls back too far as everything cools. The giveaway is movement rather than steady decline.
The pressure relief valve is passing
The pressure relief valve vents water if the system goes over pressure, through a small pipe discharging outside near the boiler. Debris on the seat can leave it weeping, and the system slowly bleeds itself down.
There is a leak in pipework you cannot see
Heating pipes run under floors, through screed and inside walls. A pinhole in a buried run can drop the pressure without ever producing a puddle, because the screed soaks the water up as fast as it arrives. That is why the code returns after every top-up with nothing to see.
| Cause | What you notice | Who deals with it |
|---|---|---|
| Air bled out, not replaced | One drop after bleeding radiators, then the pressure holds | You, with the filling loop |
| Expansion vessel | Pressure climbs while the heating runs, then falls back low | Gas Safe registered engineer |
| Pressure relief valve passing | Water dripping from the small outside pipe near the boiler | Gas Safe registered engineer |
| Leak in the sealed circuit | Steady loss with nothing visible, sometimes a warm patch on the floor | Leak detection, then a repair |
Who to call, and when it is not a leak job
E119 sends plenty of people looking for a leak detection company when they need a heating engineer. The split is clear.
- A boiler that will not fire, an ignition fault, a suspected pressure switch fault, or a gauge that disagrees with the display: a Gas Safe registered heating engineer. Anyone you pay to work on a gas appliance must be on the Gas Safe Register, and you can check their ID card against it.
- An expansion vessel that needs recharging or replacing, or a pressure relief valve that needs changing: the same engineer. Those are boiler parts.
- Pressure that keeps falling after the boiler and its parts have been checked, with no visible source: leak detection on the heating circuit.
We do not repair boilers, fit parts or service heating systems. We find water escaping from pipework unseen, then hand your plumber the exact spot to open up. Where an insurer is involved, Confused.com and MoneySuperMarket both describe trace and access cover as paying to find the leak and make good the damage caused by the search, but not the repair itself. Limits vary by policy, commonly capped around £5,000.
What a hidden heating leak actually looks like
Buried heating leaks rarely announce themselves, and the signs are easy to explain away.
- A patch of floor that feels warmer than the floor around it while the heating is on.
- Skirting, carpet or plaster that stays damp with no obvious source above it.
- A musty smell in one room that gets stronger when the heating runs.
Finding one without lifting floors is what the equipment is for. Thermal imaging picks out hot water tracking through a slab, acoustic sensors listen for water escaping under pressure, tracer gas (a non-toxic, non-flammable mix of 5% hydrogen and 95% nitrogen) goes into the drained circuit and is picked up where it surfaces, and moisture meters confirm what is genuinely wet. Our guide on how to find a leak in a central heating system explains how they work together.
Buried heating pipes in Cornwall and Devon homes
Two things about the housing stock down here make a heating leak harder to spot. The first is solid floors: the slab under an old granite or cob cottage, or the screed poured into a later extension. Both bury pipework in material that soaks water up and holds it, so nothing shows at the surface until a fair amount has gone.
The second is how often properties sit empty. Second homes and holiday lets are shut up for weeks, so a slow loss runs on until someone arrives to a cold building and an E119 on the display. We see it most autumns, when systems that sat quiet since spring are asked to work again.
Frequently asked questions
What does E119 mean on a Baxi boiler?
E119 is a low water pressure fault. Baxi and Potterton manuals list it as the water pressure switch not operating, and say it appears when the primary water pressure falls below 0.5 bar, so the boiler stops. Potterton user guides are published by Baxi Heating UK Ltd, which is why both brands share the code.
Can I fix an E119 fault myself?
Usually, yes. Topping the system back up through the filling loop or the Easy-Fill lever is a normal homeowner job and clears the code in a few minutes. Opening the boiler casing is not, and anything beyond repressurising needs a Gas Safe registered engineer.
Why does my Baxi keep showing E119?
Because the pressure is not staying where you put it. A sealed system does not use water up, so if it keeps falling there are four usual explanations: air recently bled out, a tired expansion vessel, a pressure relief valve passing water, or a leak in the circuit.
What pressure should a Baxi boiler be set to?
Typically around 1 to 1.5 bar when the system is cold, though the figure varies between model ranges. Check the safe band marked on your gauge, or the manual that came with the boiler, rather than a general number in an article.
Is E119 the same as E118?
They point at the same condition. E118 is also a low water pressure code, and which one you see depends on the model range, not on a different fault. Either way the first response is the same: check the gauge and repressurise to the cold range for your boiler.
Does E119 always mean a leak?
No. An E119 can be a one-off after radiators have been bled, or the occasional top-up Baxi says all boilers need. It points towards a leak when the pressure falls again soon after a top-up, the boiler and its own parts have been checked, and nothing visible explains where the water went.
Do I need a Gas Safe engineer for an E119 fault?
Not for the repressurising itself, which is a homeowner task. You do need one if the code stays on with the gauge reading normally, if the boiler will not fire afterwards, or if the expansion vessel or pressure relief valve is the cause.
Topped it up more than twice this month?
Pressure that keeps falling with nothing visible on the floor means water is leaving a sealed circuit, and that is the leak we trace across Cornwall and Devon without taking your floors up. If your last top-up has held, there is no leak and you do not need us.
Call Dickie on 07822 025 911