Baxi Combi No Hot Water: Codes and Common Causes
On this page (6 sections)
The Short Answer: A Baxi “tankless” heater is a combi boiler. It heats tap water on demand from the same burner that heats the radiators. When the hot water stops, the display code usually points to the cause. E118 means low system water pressure, E133 means a gas supply or ignition fault, and E125 means a circulation fault. Fix the cause, reset once, and call a gas engineer if the code comes back.
How a combi makes hot water
A combi has a sealed heating circuit filled with water, a pump, a diverter valve and a plate heat exchanger. When you open a hot tap, the diverter switches the burner’s heat from the radiators to the plate, which heats mains water as it passes through. Because tap water depends on the heating circuit working, low system pressure or a seized pump can stop hot water even though the fault has nothing to do with the tap water side.
Baxi codes linked to no hot water
The meanings below are from Baxi’s published error-code list for its combi and system boilers. Some displays show the code in two parts, such as “E1” followed by “33”. Confirm the code against the user guide for your model, because older and non-UK models may differ.
| Code | Baxi’s description | What it usually means for you |
|---|---|---|
| E118 | Water pressure low (below 0.5 bar) | Check the pressure gauge. If it keeps dropping, the system is leaking |
| E133 | Gas supply fault; Baxi lists power supply, sensing electrode, spark electrode and cable as checks | Gas off or interrupted, or an ignition fault. A frozen condensate pipe can also cause lockouts on condensing boilers |
| E125 | Water circulation fault | Pump, air or sludge in the heating circuit. Needs an engineer |
| E110 | Maximum temperature exceeded (probable jammed pump or air), or safety thermostat tripped | Overheating. Don’t keep resetting it |
| E160 | Fan fault | Needs an engineer |
| E20 / E28 / E50 | Heating, flue or hot-water temperature sensor faults | A sensor or wiring repair |
| E130 | Flue thermostat tripped (lockout) | The flue overheated. Needs an engineer |
| E270 | Dry fire | Stop and call an engineer |
If your Baxi shows a code that isn’t in this table, don’t assume it matches a code from another brand. Rinnai, Navien and other tankless codes use different numbering.
What you can check before calling
- The pressure gauge. Most Baxi user guides give a normal cold reading of roughly 1 to 1.5 bar. A reading near zero matches an E118 code. Many Baxi user guides show owners how to top up pressure with the filling loop. If yours does, follow it exactly. If the pressure drops again within days, there is a leak somewhere, such as a radiator valve, the pressure relief pipe outside, or a fault inside the boiler, and an engineer needs to find it.
- Gas to the property. Check whether your hob or other gas appliances work. On a prepayment meter, check the credit. A gas outage or empty meter will produce an ignition lockout.
- The condensate pipe in freezing weather. On condensing models, a frozen outdoor condensate pipe can lock the boiler out. Baxi’s user guides describe thawing it with warm (not boiling) water poured on the outside of the pipe. Then reset once.
- Whether heating works. If radiators heat but taps stay cold, the diverter valve, the hot-water flow sensor or the plate heat exchanger is the likely cause. If neither works, look at pressure, gas and the codes above.
- Reset once. After fixing an obvious cause, use the reset button described in the user guide one time. Repeatedly resetting an E133 lockout makes the boiler keep trying to light without fixing anything.
What the engineer will look at
A Gas Safe registered engineer (UK) or licensed gas technician will check the gas pressure at the boiler. They will inspect the spark and sensing electrodes and the flue, check the fan and pump, and test the temperature sensors. Where hot water is weak or temperatures swing, they will check the diverter and the plate heat exchanger for scale. In hard-water areas, a scaled plate exchanger is a common cause of lukewarm or fluctuating hot water. It can usually be replaced on its own.
Repair or replace?
Sensors, pumps, fans, diverter valves, electrodes and plate heat exchangers are routine parts on most Baxi combis. Replacement becomes worth considering when the main heat exchanger leaks or has failed, when the boiler needs several major parts at once, or when parts for an older model are no longer available.
Frequently Asked Questions
Q: Radiators are hot but the taps are cold. What’s wrong? A: The boiler is lighting, so gas and ignition are working. A diverter valve stuck in the heating position, a faulty hot-water flow sensor, or a blocked plate heat exchanger are the usual causes. All of these are engineer repairs.
Q: Why does my Baxi keep losing pressure? A: Water is escaping somewhere. Check radiators, valves and visible pipes for drips, and look at the pressure relief pipe outside for signs of discharge. If you can’t find the leak, or the relief pipe is discharging, an engineer needs to check the expansion vessel and the boiler internals.
Q: Is Baxi E133 the same as Rinnai code 11? A: Both relate to ignition, but each brand defines its own codes and fault checks. Use Baxi’s own code list for a Baxi.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- Baxi: boiler error codes (trade technical support) (opens in a new tab)Baxi combi and system boilers listed on the page, including the 200, 400, 600 and 800 series, Platinum, Duo-tec, EcoBlue and Assure ranges.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
- CPSC: carbon monoxide fact sheet (opens in a new tab)Carbon monoxide hazards and emergency response.
Editorial standards and corrections · Prepare a useful service request