Top 10 Boiler Installation Mistakes (and How to Avoid Them)
Even the best boiler can underperform if installed incorrectly. From pipework errors to poor commissioning, small mistakes can cost energy and reliability. Our Gas Safe engineers at ARA Services Ltd explain the most common faults and how to avoid them. If you’re planning an upgrade, read our guide on how much a new boiler installation costs in 2025.
Why Correct Installation Matters
Proper installation ensures efficiency, safety, and warranty validity. Mistakes increase fuel bills, shorten lifespan, and may void manufacturer cover. Discover why a high-efficiency boiler still needs correct setup to perform at its best.
Schedule a Safe InstallationTop 10 Boiler Installation Mistakes
- Incorrect boiler sizing — undersized units struggle; oversized waste energy. Always run a professional heat-loss calculation.
- No system flush — sludge left in radiators reduces efficiency and damages new components.
- Missing magnetic filter — leads to debris buildup and early breakdowns.
- Poor flue placement — breach of regulations and risk of exhaust re-circulation.
- Wrong condensate pipe fall — causes freezing and shutdown in winter.
- Ignoring manufacturer settings — flow temps, pump speeds, and controls must be configured per manual.
- Improper gas pressure — affects combustion efficiency and safety; must be tested with a manometer.
- No inhibitor added — leads to corrosion inside the system.
- Poorly sealed joints — water leaks corrode parts and flooring.
- No benchmark certificate — without it, the warranty and building-reg compliance are invalid.
How to Avoid These Issues
- Use only Gas Safe-registered engineers.
- Request a full power flush before fitting.
- Ensure installer completes and signs the Benchmark Certificate.
- Check for correct flue clearance and condensate routing.
- Book an annual boiler service to protect warranty and efficiency.
To avoid costly repairs and wasted energy, learn how a new boiler can lower heating bills and improve system efficiency.
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FAQs
Can I install my own boiler?
No — boiler installation must be completed by a Gas Safe-registered engineer to meet UK law.
What’s the most common mistake?
Failing to flush the heating system and fit a magnetic filter is the most frequent cause of early faults. Learn why this matters in our boiler servicing guide.
Do I need building-reg certification?
Yes. A compliance certificate should be filed with Gas Safe Register after every installation — often handled by your installer when using a trusted boiler brand.