The 7 signs we look for
- Age — 10+ years old (modern A-rated boilers are 30% more efficient)
- Rising gas bills with no change in usage
- More than one breakdown per year
- Yellow or sooty flame (should be sharp blue)
- Visible water leaks from the boiler body
- Kettling, banging or rumbling sounds when firing
- Repair parts on long lead-times or discontinued
When to replace vs. repair
Rule of thumb — if a single repair quote is over €500, or you've spent more than €400–500 on repairs in the last 12 months, replacement usually pays for itself within 3–4 years through lower gas bills.