Hot water cylinder replacement and unvented cylinder installation

Replacing a tired hot water tank, or moving to mains-pressure stored hot water.

Gas Safe registered (554328) Worcester Bosch accredited Free, no-obligation quotes

What we offer

A hot water cylinder rarely gets much thought until it starts leaking, runs out of hot water too soon or makes the morning shower a trickle. Replacing it is a chance to choose between a like-for-like vented cylinder fed from a cold water tank in the loft, and an unvented cylinder that runs at mains pressure. The right answer depends on your water supply, your boiler and how your household uses hot water.

We are G3 qualified and we fit Megaflo, Telford and Joule cylinders. John The Plumb is also Gas Safe registered (554328) and a Worcester Bosch accredited installer, so the cylinder and the boiler can be planned as one system. A free in-home survey checks your supply and space, followed by a fixed price in writing.

Vented and unvented cylinder replacement
G3 qualified unvented installation
Megaflo, Telford and Joule cylinders
Mains pressure and flow checked first

Get a free quote 07891 410 960

Hot water cylinder replacement and unvented cylinder installation

Vented or unvented?

A vented cylinder is fed by gravity from a cold water storage tank, usually in the loft, so the pressure at your taps depends on how high that tank sits. An unvented cylinder is fed directly from the mains and stores hot water at mains pressure, giving stronger showers and allowing the loft tanks to be removed. Vented cylinders remain a sensible, simpler choice where the mains supply is weak or the household is happy with current performance. The survey sets out both options for your home.

Checking pressure and flow first

An unvented cylinder can only deliver what the incoming mains can supply. Before recommending one, we measure the mains pressure and, just as importantly, the flow rate, ideally with other outlets running to see how the supply holds up. The size of the incoming water pipe matters too, especially in older properties. If the supply is not strong enough, an unvented cylinder will disappoint, and we would rather tell you that at the survey than after it is fitted.

Discharge pipework and safety

Unvented cylinders store water under pressure, so they carry safety devices including temperature and pressure relief valves and an expansion vessel. If a valve ever opens, hot water must be carried safely away through discharge pipework that follows set rules on size, route and termination. This is why unvented installation is restricted to G3 qualified installers and must be notified under Building Regulations. Planning the discharge route is often what decides where the cylinder can go.

When a system boiler and cylinder beats a combi

A combi heats water on demand, which suits smaller homes with one bathroom. Where two or more showers run at once, or a household simply uses a lot of hot water, a system boiler with an unvented cylinder can serve several outlets at mains pressure without the flow dropping off. It does need space for the cylinder. If your boiler is also due for replacement, the survey looks at the whole hot water arrangement rather than the cylinder in isolation.

Looking after a new cylinder

Unvented cylinders should have their safety devices checked annually, and manufacturers set out maintenance requirements in their documentation; keep the paperwork and benchmark records together. In hard water areas, scale builds up on immersion heaters and heating coils over time. On the day, the old cylinder is drained and removed, the new cylinder and controls are fitted, and the system is filled, tested and commissioned, with the controls explained at handover.

FAQs

Frequently asked questions

Do I need a G3 qualified installer for an unvented cylinder?+

Yes. Unvented hot water cylinders must be installed by someone holding the relevant unvented qualification, known as G3, and the work must be notified under Building Regulations. We are G3 qualified.

How long does a hot water cylinder last?+

It depends on the cylinder type, water quality and how well it has been looked after. Signs it may need replacing include leaks, corrosion around the connections and hot water that runs out more quickly than it used to.

Can my water pressure support an unvented cylinder?+

That depends on both mains pressure and flow rate at your property. We test both during the free survey before recommending an unvented cylinder.

Related services

How unvented cylinders work Converting vented to unvented Unvented vs vented cylinder Unvented cylinder safety checks Mixergy smart cylinder installation Boiler replacement

Plan your new hot water cylinder

Book a free survey to test your supply and compare vented and unvented options, with a fixed written quote.

Get a free quote 07891 410 960