Common problems guide

The most common Vaillant ecoFIT Pure 830 problems

The faults most likely to send a Vaillant ecoFIT Pure 830 into lockout — with plain-English causes, what to check first, estimated repair costs and whether you need a Gas Safe engineer.

52 documented codes
6 most common
1 DIY-safe checks
5 engineer needed

The 6 most common faults

01
F.22 High DIY-safe

Your boiler has stopped working because the water level inside the system is too low to operate safely.

What to try first

Locate the filling loop (a flexible silver hose) underneath your boiler, often found near the pipework connections.Open the valves on both ends of the loop to allow mains water into the system until the pressure gauge on the front of the boiler reads between 1.0 and 1.5 bar.Turn off both valves tightly to stop the flow of water and ensure the loop is not leaking.

Est. cost
£60-120
Parts
Pressure Relief Valve (PRV), Expansion Vessel, Pressure Sensor
Full guide for F.22
02
F.00 High Engineer

Your boiler has lost its connection to the sensor that measures how hot the internal water is, so it has turned itself off as a precaution.

Est. cost
£150-250
Parts
NTC flow temperature sensor, Wiring harness
Full guide for F.00
03
F.01 High Engineer

Your boiler has lost the signal from one of its internal temperature sensors, causing it to stop heating to prevent potential damage.

Est. cost
£120-220
Parts
Return temperature sensor, Wiring harness
Full guide for F.01
04
F.10 High Engineer

Your boiler has stopped working because one of its internal temperature measurement sensors is malfunctioning or its wiring has disconnected.

Est. cost
£120-200
Parts
NTC Flow Temperature Sensor, Wiring harness
Full guide for F.10
05
F.11 High Engineer

Your boiler has detected an electrical fault with the internal sensor that monitors the temperature of the water returning to the system, causing it to shut down for safety.

Est. cost
£120-200
Parts
Return temperature sensor, Wiring harness
Full guide for F.11
06
F.20 High Engineer

Your boiler has detected that it is getting too hot and has automatically shut down to prevent damage or overheating.

Est. cost
£120-250
Parts
NTC Thermistor, Pump, Heat Exchanger
Full guide for F.20
Parts most often replaced

on the Vaillant ecoFIT Pure 830

Pressure Relief Valve (PRV)Expansion VesselPressure SensorNTC flow temperature sensorWiring harnessReturn temperature sensor

Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.

Call a Gas Safe engineer if…

  • You can smell gas or see signs of a leak
  • The Vaillant shows an Emergency or High severity code
  • The boiler keeps locking out after repeated resets
  • You've tried the DIY checks and the fault hasn't cleared
  • There's visible water leaking from the boiler
  • The flame is yellow or orange instead of blue
See the full 52-code list for the Vaillant ecoFIT Pure 830

Related guides

Boiler losing pressure → No hot water → When to replace → Symptom checker →