Unvented hot water cylinders provide efficient, high-pressure hot water for UK homes, especially electric mains pressure models from brands like Ariston, Eldom, TTulpe, Quality Heating and more. Regular servicing ensures safety, efficiency, and compliance with Building Regulations Part G3. This guide outlines how to service unvented hot water cylinders annually – but remember, only a qualified G3 engineer can perform these tasks legally and safely.
Why Annual Servicing Matters for Unvented Cylinders
Servicing prevents limescale buildup, valve failures, and pressure issues, common in hard water areas across England and Wales. It can reduce energy costs by up to 20% and extend cylinder life to 10-15 years. Crucially, annual unvented hot water cylinder servicing is required to maintain your warranty – Ariston and Eldom policies void coverage without proof of professional checks. Neglect could lead to leaks, bursts, or invalid insurance claims.
Who Can Service Unvented Hot Water Cylinders?
Only G3-qualified engineers (certified by BPEC or City & Guilds) are authorised to service unvented systems due to high-pressure risks. DIY or unqualified work is illegal and dangerous. A G3 engineer uses specialist tools for safe pressure discharge and diagnostics. We recommend booking your annual service with a local G3 engineer to ensure compliance.
Step-by-Step Guide: How to Service Unvented Hot Water Cylinders
Follow these steps during your annual unvented cylinder service. Schedule with a G3 professional for compliance.
1. Prepare and Isolate the System
- Turn off the power supply at the fuse board and isolate the water supply.
- Drain the cylinder using the drain cock at the base, relieving pressure safely.
2. Inspect and Test Safety Valves
- Check the temperature and pressure relief (T&P) valve: Lift the lever to discharge water, ensuring free flow and no drips on reset.
- Test the pressure relief valve for blockages – essential for preventing over-pressurisation.
3. Examine the Expansion Vessel
- Test air charge (0.75-1.5 bar when empty) with a gauge.
- Drain and check for waterlogging; replace if faulty to absorb expansion.
4. Flush and Descale the Cylinder
- Flush sediment and limescale from the tank. Use a descaling solution in hard water regions.
- For electric models, inspect the immersion heater for efficiency.
5. Check Electrical and Thermostat Components
- Verify thermostat at 60°C max to avoid scalding and Legionella.
- Inspect wiring, connections, and heating elements for corrosion.
6. Inspect for Leaks and Corrosion
- Examine joints, casing, and pipework for dampness or rust.
- Tighten connections as needed.
7. Recharge and Test
- Refill the system, bleed air, and restore power.
- Run a full system test to confirm balanced pressure and hot water flow.
Brands like Ariston (e.g., Andris Lux) and Eldom (e.g., 60-100 DU series) recommend these exact checks in their manuals to uphold performance and warranty.
Common Issues and Prevention
- Limescale: Install a water softener in hard areas.
- Valve Failure: Annual tests catch early wear.
- Warranty Tips: Keep service records showing G3 certification.
Schedule Your Unvented Cylinder Service
As a supply-only specialist, Aizo Quality Heating provides premium unvented hot water cylinders, including Ariston and Eldom models. For expert unvented hot water cylinder servicing, book with a certified G3 engineer in your area to protect your system and warranty. Visit qualityheating.co.uk for more on unvented cylinder maintenance UK, electric water heaters, and G3 compliance.