Potterton E119 fault codewhat it means and how to fix it
The sealed system on a rotary-switch Potterton — Promax, Titanium, Gold, Heatmax — has dropped below half a bar. The window shows E1 and then 19. Fill to 1–1.5 bar and it clears itself.
Take care
How often does the Potterton need topping up?
The right answer depends on what you can see. Pick the one that matches.
Choose the option on the left that matches what your appliance is doing, and the answer for that case appears here.
First time, or once a year
Normal for a sealed system. Fill and carry on.
Nothing further unless it recurs within a few weeks.
Every few weeks
The guide's "regular re-pressurising" — a leak, or an expansion vessel that has lost its charge.
Tenants: report it in writing with the dates. Owners: book a leak trace and vessel check.
Gauge is above 1 bar but E119 stays
The switch or its wiring, not the water. The boiler cannot see the pressure the gauge shows.
Engineer: a quick diagnosis and a cheap part.
What E119 means
Every Promax, Titanium and Gold manual from 2007 to 2017 defines the code by a single threshold, and the sentence does not change between ranges: the primary circuit has fallen below half a bar. The table row behind it names the water pressure switch as the part that has not operated, which tells you how a Potterton knows — a switch on the hydraulic block that stays open until there is enough water behind it.
Potterton write the user guides for a householder who has never touched a boiler, so the E119 paragraph adds something the other codes do not get: once the system is back up to pressure the boiler is expected to run again, and the installer is named as the person to ask about how to repressurise. The repressurising section that follows it is unusually specific about Potterton hardware. The filling loop supplied with these boilers is not a braided hose left in place; it is two blue-handled isolating taps under the right-hand side of the boiler with a separate temporary filling pipe that must be connected for the top-up and removed afterwards, blanking caps refitted.
Many installers fitted a permanent loop on the pipework instead, so look for either. The Potterton installed base is heavily rented and social housing, and the relevant point for a tenant is that E119 is not a repair: the user guide gives you the procedure, and a boiler that needs it more than a couple of times a season is what you report.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Water has left the system somewhere | The Promax user guide says it plainly: pressure below 0.5 bar "may indicate a leak on the central heating system", and "if the water pressure requires regular re-pressurising a fault or leak is indicated". Gland nuts on radiator valves, a corroded panel, a fitting under the floorboards. | Common |
| Expansion vessel has lost its charge | With no air cushion the pressure climbs to 3 bar on heating and the relief valve lets water out through the wall. By morning the gauge is under 0.5 bar again. A common finding on a Promax past ten years old. | Common |
| Switch contacts not closing, or the lead to them | Section A of the Promax fault-finding chart: with the gauge reading over half a bar and E119 still up, check the switch connection (COM–NO to PCB connector X400) and replace the water pressure switch, part 5114748 in the Promax Combi parts list. | Occasional |
| Air worked out of a newly filled system | After a repair or a radiator change the pressure drops as trapped air bleeds off. One further top-up is expected; the user guide's "regular" is the threshold for calling someone. | Occasional |
What to try yourself
With the boiler cold, read the pressure gauge on the front panel. The Promax and Titanium user guides want at least 0.5 bar cold and normally 1 to 1.5; the green sector on the gauge runs from 1 to 2.5.
Look underneath the right-hand side of the boiler for two blue-handled taps. If they carry blanking caps, remove the caps and fit the temporary filling pipe between them, flanged washers at both ends, wing nuts tightened. If a permanent loop with two valves is fitted on the pipework instead, use that.
Fully open one blue tap first, then open the second slowly while watching the gauge. When the needle is between 1 and 2 bar, close both taps.
Do not go above 2.5 bar. At 3 bar the safety valve opens, and Potterton's guide treats that as a fault to report to your installer.Remove the temporary pipe, refit the blanking caps and keep the pipe somewhere you will find it. Leaving it connected is the mistake Potterton's guide warns about, because a passing tap can then flood the system to the relief valve.
The display should return to the temperature. Do not turn the selector to Reset; the reset does not act on E119. Note the date so you know how long the fill lasts.
Get a Gas Safe registered engineer to look at your Potterton E119
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What it costs to fix
Typical repair cost
£0–£300
Time on site
10 minutes
Nothing to top up. Water pressure switch replaced £110–£170. Expansion vessel recharge £80–£120, replacement £180–£300. Leak trace from £90.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Parts you may need
We may earn a commission if you buy a part through one of these links. It does not change what you pay, and it does not affect which parts we list.
Expansion vessel (8 litre, sealed system)
EV-8L£35–£85Plumbing merchant
Price checked 28 September 2026
Pressure relief valve, 3 bar
PRV-3B£18–£42Plumbing merchant
Price checked 28 September 2026
Baxi / Potterton / Main hydraulic pressure switch (600, 800, Assure, Eco Compact)
5114748£40–£90Authorised Baxi parts distributor
Price checked 28 September 2026
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Potterton fault codes
- E118Get it checkedThe digital-display Pottertons — Assure Combi, Assure System, Promax Ultra — have dropped below half a bar on the heating circuit. Repressurise to 1–1.5 bar and the boiler restarts on its own.Related: water pressure
- E117Get it checkedPrimary water pressure above 2.7 bar on the Potterton Promax Ultra. Usually an over-filled system or a failed expansion vessel; an engineer should let it down and find out which.Related: water pressure
- E133Get it checkedGas supply interrupted, ignition failed or no flame detected — every Potterton generation. Confirm the gas supply, one reset (5 s on the knob, 1–3 s on the button), and call if it returns.Related: same brand
- E110Get it checkedSafety thermostat operated — the primary water overheated — on every Potterton code display. One reset is permitted (5 s knob or 1–3 s button); a second E110 is a circulation fault for an engineer.Related: same brand
- E125Get it checkedCirculation fault (primary circuit) on every Potterton code display — the water did not warm as expected after lighting, or overshot twice. Pump, air or sludge; an engineer job after one reset.Related: same brand
- E128Get it checkedFlame failure during normal operation on the Potterton Assure and Promax Ultra: the burner was lit and went out. Resettable; recurring E128 wants an engineer.Related: same brand
Own a Potterton boiler? Save it and its codes come first next time.
Related guides
Common questions about Potterton E119
The display flashes E1 and then 19. Is that two faults?
One. The window shows two characters, so Potterton split the code: "code E133 will be displayed by 'E1' alternating with '33'" is the example in the user guide, and E119 follows the same pattern.
My Potterton Assure shows 118, not E119. Same thing?
Same fault — the primary circuit below half a bar — but a different generation with a different display. The Assure and Promax Ultra pages for 118 apply to you.
I cannot find a filling loop under the boiler.
On a Promax the loop is two blue-handled taps with a separate pipe that the installer may have taken away or left in the cupboard. If there are no taps under the boiler, the loop is on the pipework nearby; if there is nothing at all, an engineer will need to bring one.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.