Fill the installation
The F22 error code on Heatline boilers indicates fill the installation.
Heatline F22 means: fill the installation. The usual causes are leaking heat exchanger (corrosion or thermal stress cracks), failed pump seal or loose pipe connections within the boiler. You can safely reset the boiler once — if F22 returns, do not keep resetting. A qualified heating engineer should diagnose the root cause.
What Does F22 Mean
The F22 code is shown by the boiler’s control board when it detects fill the installation. The boiler then stops instead of continuing to run in that condition: the code is the appliance reporting a problem, not proof that the boiler is broken.
| What you see on the boiler |
|---|
| The display shows F22 and the boiler stops until the fault is cleared |
Common Causes
Causes documented in 2 technical sources.
| Cause |
|---|
| Leaking heat exchanger (corrosion or thermal stress cracks) |
| failed pump seal |
| loose pipe connections within the boiler |
| faulty pressure relief valve dripping |
| failed O-rings or gaskets |
| condensate pipe connection leak |
Safety Warning
F22 involves electrical or pressure-related components. Do not attempt repairs without proper qualifications. Ensure the boiler is electrically isolated before any inspection. If you notice water leaks, unusual sounds, or pressure anomalies, contact a qualified heating engineer immediately.
Parts & Prices
Prices shown are indicative. Actual prices and availability vary by region.
Step-by-Step Diagnosis
Open the boiler casing and identify the source of the leak — use a torch and tissue paper to trace it
Check the heat exchanger for signs of corrosion or green verdigris deposits
Inspect the pump for water around the shaft seal
Check all internal pipe connections and joints
Check the pressure relief valve discharge pipe
Inspect the condensate trap and drain connections
How to Fix It
Tighten any loose connections
replace failed O-rings or gaskets
replace the pump if the seal has failed
if the heat exchanger is leaking, it typically needs replacement (or the whole boiler if it is old)
replace the pressure relief valve if dripping
Refer to the Heatline service documentation for the detailed procedure. Only a qualified engineer should carry out these repairs.
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Affected Models
Heatline models that can display fault code F22:
| Model Family | Output Range | Frequency |
|---|---|---|
| All Heatline models | — | Possible |
Frequently Asked Questions
Tighten any loose connections. According to the technical documentation, this is the first check on the list for F22.
F22 is not classified as a high-severity fault, so the boiler can be reset once. If F22 comes back, stop resetting: the underlying cause is still there and needs a qualified heating engineer.