Top 10 Warning Signs
1. Age Over 15 Years
Why it matters: Parts become unavailable, efficiency drops, breakdown risk increases
Action: Budget for replacement within 12 months
2. Frequent Repairs
Rule of thumb: If repairs cost more than 50% of a new boiler in a year, replace it
- Repairs every few months
- Same problem recurring
- Multiple engineer visits per year
Annual repair costs exceeding £500? Time to replace.
3. Rising Energy Bills
Efficiency decline: Old boilers lose 3-5% efficiency per year
Old Boiler (60% efficient):
£1,600/year heating costs
New Boiler (94% efficient):
£1,000/year (£600 savings!)
4. Strange Noises
- Banging/clunking: Limescale buildup, failing pump
- Whistling (kettling): Limescale in heat exchanger
- Gurgling: Air in system or sludge
- Whirring: Fan bearing failure
Persistent noises despite repairs indicate internal deterioration.
5. Slow to Heat or Cold Spots
- Radiators take longer to warm up
- Some radiators stay cold
- Inconsistent hot water temperature
- Boiler takes ages to fire up
Try powerflush first, but if problem persists, boiler is struggling.
6. Yellow Flame (Not Blue)
Healthy flame: Crisp blue
Dangerous flame: Yellow, orange, or sooty
Turn off boiler immediately and call Gas Safe engineer
7. Water Leaks
- Pooling water around boiler
- Dripping from pipes or boiler casing
- Pressure drops frequently
- Corrosion visible on boiler
Small leaks can be repaired, but persistent leaking indicates internal corrosion or seal failure.
8. Constant Pressure Loss
If you're topping up pressure weekly:
- Internal leak in heat exchanger
- Expansion vessel failure
- Pressure relief valve stuck
Repairs expensive and often temporary on old boilers.
9. Unreliable - Cuts Out Often
- Boiler shuts down randomly
- Won't fire up when thermostat calls for heat
- Error codes appearing frequently
- Pilot light keeps going out
Intermittent faults indicate electronic control failure or sensor issues.
10. Parts No Longer Available
Boiler manufacturers typically support models for 10-12 years. After that:
- Spare parts discontinued
- Engineers refuse to service
- Insurance/warranty void
No parts = no choice but replacement
Repair vs Replace Decision
| Factor | Repair | Replace |
|---|---|---|
| Age | Under 10 years | Over 12 years |
| Repair Cost | Under £300 | Over £500 |
| Efficiency | 85%+ | Below 80% |
| Frequency | First breakdown | 3+ breakdowns/year |
| Parts | Available | Discontinued |
Replacement Costs 2025
Budget Range
£1,500
Basic combi boiler
Mid Range
£2,500
Quality brand combi
Premium
£4,500
System boiler + cylinder