Unvented cylinder installation, G3 qualified
An unvented cylinder holds stored hot water at mains pressure, which is why the law puts it in a category of its own. Jamie holds the G3 unvented hot water qualification and installs cylinders across Shefford, Bedfordshire, Hertfordshire, Buckinghamshire and the Cambridge area.
Why the qualification is not optional
An unvented cylinder is fed straight off the cold mains and stores water under that pressure. Get the safety arrangement wrong and the failure modes are serious, which is why Part G of the Building Regulations treats it differently to almost anything else a plumber touches.
Under section G3, any unvented hot water storage vessel over 15 litres has to be installed, commissioned and serviced by someone holding a recognised G3 qualification. It is also notifiable building work. Jamie holds that qualification, so the cylinder in your airing cupboard is fitted by somebody legally entitled to fit it.
What people get wrong about unvented cylinders
Most of the bad installations that turn up are not dramatic. They are a discharge pipe run at the wrong fall. They are a tundish buried behind boxing where nobody will ever see it discharging. They are an expansion vessel that lost its charge years ago and has never been touched since. None of those stop the hot water working, which is exactly why they go unnoticed.
The safety devices are the job
Expansion vessel, temperature and pressure relief valve, expansion valve and energy cut-out. They are what stands between stored water at mains pressure and a very bad day.
Discharge pipework done properly
A visible tundish, a continuous fall and a safe termination point outside. If you cannot see the tundish, you cannot see the system telling you something has failed.
Serviced rather than forgotten
The safety devices degrade quietly. An annual check is the only thing that finds a tired relief valve or a flat expansion vessel before it matters.
How an unvented cylinder install runs
A cylinder swap is not a like for like lift and shift. The system around it has to be right before the vessel goes anywhere. This is the order the work goes in.
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1
Check the mains will carry it
An unvented system is only as good as the cold mains feeding it. Pressure and flow rate both get measured before anything is specified, because a cylinder sized for a supply the house does not have will disappoint every morning.
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2
Size the cylinder to the household
Number of bathrooms, how many people and when they all want hot water at once. Undersize it and you run out. Oversize it and you are paying to keep water hot that nobody uses.
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3
Strip out and set the position
The old vessel comes out along with any redundant tanks and pipework. The new cylinder is set level on a solid base with proper access left around the controls, because everything on it needs to be reachable for servicing.
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4
Safety devices and discharge pipework
Expansion vessel, relief valves and cut out are fitted and set correctly, then the discharge is run through a visible tundish with a continuous fall to a safe termination outside. This is the part of the job the regulations exist for.
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5
Fill, commission and hand over
The system is filled, vented, brought up to temperature and the safety devices are tested. You get the paperwork, the notification route confirmed and a straight explanation of what to look for between services.
The cylinder work Jamie covers
New installations, replacements and the safety side of a system that is already in.
New unvented cylinders
Sized to the household and the mains supply, installed and commissioned under Jamie's G3 qualification.
Cylinder replacements
Old vessels swapped out, with the pipework and controls around them brought up to the current arrangement rather than reconnected as found.
Annual servicing
Safety devices checked and the expansion vessel recharged. The only thing that catches a failing component before it becomes a problem.
Discharge pipework corrections
Buried tundishes, insufficient fall and unsafe termination points put right on systems that were never set up correctly.
Immersion heaters
Immersion elements and their thermostats replaced where they have failed or scaled up on an existing cylinder.
Leaks on cylinder pipework
Weeping connections and failed valves on the pipework serving the cylinder. See burst pipe repair and leak detection.
Cylinder needs replacing or checking over?
Tell Jamie what is in the cupboard now and what the house needs from it. Scope and price agreed before anything comes out.
Is an unvented cylinder right for your house
Unvented systems are the default answer for most modern installations, though they are not automatically the right choice for every property. A few things decide it.
Your cold mains has to be up to it
The whole point of an unvented cylinder is mains pressure at the taps, so the mains has to deliver enough pressure and enough flow. A long run of old lead or narrow bore supply pipe will limit what any cylinder can give you. It gets measured rather than assumed.
Space, access and the discharge run
The cylinder needs a solid base, room around the controls for servicing and a route for the discharge pipe to reach a safe termination outside. An airing cupboard in the middle of a house with no external wall nearby makes that run considerably harder.
Notification and paperwork
Installing or replacing an unvented cylinder over 15 litres is notifiable building work in England and Wales. It is either notified directly to Local Authority Building Control or self certified through an approved competent person scheme. The route for your job is confirmed with you before the work starts so you know what paperwork you are getting.
Keep the service up
An unvented cylinder should be checked annually. The relief valves, the expansion vessel and the cut out all degrade slowly and silently. The service is what finds them. It also keeps most manufacturer warranties intact.
What it costs
Cylinder work prices vary with the vessel, the state of the existing pipework and the discharge run, so there is no useful figure to quote in advance. Every job is priced and agreed before work starts with no hidden charges. Tell Jamie what is in the cupboard when you get in touch and he will price it properly.
Where Jamie works
Cylinder installations run across Bedfordshire, Hertfordshire, Buckinghamshire and into the Cambridge area from the Shefford base. You can check your own town on the areas we cover page, which lists every part of Beds, Herts, Bucks and Cambridgeshire Jamie travels to.
Not sure if Jamie covers your village?
The coverage hub lists every area across Bedfordshire, Hertfordshire, Buckinghamshire and the Cambridge area.
Related plumbing work
Cylinder work rarely happens in isolation. These are the pages covering the jobs that sit closest to it.
Burst pipe repair
Leaks on the pipework feeding or leaving the cylinder, traced and replaced. Read more about burst pipe repair and leak detection.
Bathroom installation
New bathrooms that ask more of the stored hot water than the old cylinder can give. Read more about bathroom installation and renovation.
General plumbing
The everyday repairs and replacements around the rest of the house. Read more about general plumbing services.
If a cylinder is discharging, leaking or has left the house with no hot water at all, the emergency plumber page covers out of hours attendance. Where the pressure problem turns out to be at the outlets rather than the cylinder, that is usually a tap or valve issue and sits under leaking tap repairs instead.
Unvented cylinder questions
Who is allowed to install an unvented cylinder?
Under Part G of the Building Regulations, an unvented hot water storage vessel over 15 litres must be installed, commissioned and serviced by someone holding a recognised G3 qualification. Jamie holds that qualification.
Does an unvented cylinder installation need to be notified?
Yes. In England and Wales it is notifiable building work, either notified directly to Local Authority Building Control or self certified through an approved competent person scheme. The route for your job is confirmed with you before work starts.
What are the safety devices on an unvented system?
An expansion vessel to take up the expansion as water heats, a temperature and pressure relief valve, an expansion valve and an energy cut out. The discharge from the relief valves runs through a visible tundish to a safe termination point outside.
Why is water dripping from the pipe outside my house?
A discharge running outside normally means a relief valve has operated or is passing, which usually points to a failed expansion vessel or a faulty valve. It is worth getting looked at rather than ignored, because the discharge is the system telling you something has gone.
How often should an unvented cylinder be serviced?
Annually. The relief valves, the expansion vessel and the cut out all degrade slowly without any obvious symptom, so the service is the only thing that finds a tired component. It also keeps most manufacturer warranties intact.
Will an unvented cylinder work in my house?
It depends on your cold mains. The system delivers mains pressure at the taps, so the incoming supply needs enough pressure and enough flow to support it. Both get measured before anything is specified rather than assumed.
Cylinder work done by someone qualified to do it
Jamie the Happy Plumber installs and services unvented cylinders across Shefford and the surrounding counties under his G3 qualification.
