Unvented Cylinder (G3) Servicing London

If your property has a pressurised mains-fed hot water cylinder, it requires a separate annual safety check under the G3 Building Regulations. This is a legal requirement for landlords and a critical safety check for homeowners, ensuring pressure and temperature relief devices function correctly. Unlike a traditional vented cylinder fed from a cold tank in the loft, an unvented cylinder works under mains pressure, which demands specialised safety components and annual professional inspection.

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Our G3-qualified engineer will check all safety-critical components, including the expansion vessel pressure, the temperature and pressure relief valves (TPRV), the factory-fitted thermostat, and the system's general condition. They will also inspect the discharge pipework to ensure it is safe and compliant. This check is not part of a standard boiler service and must be carried out by a specially qualified professional.

You receive a clear explanation of what the service involves before booking. We provide a no-obligation quote for the annual service. If any parts require replacement or additional work is needed, this will be discussed and quoted for separately, with no work proceeding without your agreement.

Our pricing for the annual G3 service is confirmed by quote, based on your specific cylinder. We do not operate fixed-price packages for this specialised work. You can view typical UK price ranges for other common services like boiler servicing on our pricing page.

What you get

Qualified: Our engineers hold the specific G3 certification legally required for working on unvented cylinders.
Compliant: The annual service fulfils the manufacturer's warranty conditions and meets legal safety obligations.
Thorough: We check the expansion vessel, temperature/pressure relief valve, thermostat, and discharge pipework.
Clear: You receive a full written report detailing the condition and operation of all safety devices.
Separate: This is a dedicated check distinct from your boiler service, which does not cover the cylinder.
Registered: All our engineers are Gas Safe registered for any associated gas appliance work.

How it works

A method, not a guess

Request a Quote

Contact us for a specific quote for the annual G3 unvented cylinder service. We will ask for your cylinder's make and model if known.

Book Your Appointment

Once you accept the quote, we will schedule a convenient appointment with one of our G3-qualified engineers.

Annual Safety Inspection

The engineer performs the full G3 check, testing all safety devices and the system's overall condition.

Report & Recommendations

You receive a full report. If any parts need replacing, you will be advised and provided with a separate quote for the repair.

Questions

Unvented Cylinder Servicing FAQs for London homeowners

What is the difference between a vented and an unvented cylinder?

A vented cylinder is fed by gravity from a cold-water tank in the loft, operating at low pressure. An unvented cylinder is connected directly to the mains water supply, operating at high pressure and requiring specific safety devices as mandated by G3 regulations.

Why is an annual G3 service a legal requirement?

The G3 Building Regulations govern the safe installation and maintenance of unvented hot water systems. The annual service checks critical safety devices like the pressure relief valve, which are essential to prevent dangerous over-pressurisation.

Is this included in my boiler service?

No. A standard boiler service does not cover the safety checks required for an unvented hot water cylinder. This must be carried out separately by a G3-qualified engineer.

Do landlords need this service?

Yes. Landlords have a legal duty to ensure all gas and water heating systems are safe. An annual G3 service is part of this duty for properties with unvented cylinders and is separate from the Gas Safety Certificate (CP12).

What if a safety device fails the check?

If a component like the pressure relief valve is faulty, it must be replaced for the system to be safe. Our engineer will explain this and provide a separate, no-obligation quote for any necessary parts and labour.

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