G3 QUALIFIED
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G3 qualified, so the install is legal and certified
Building Control notified as part of the job
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HOW IT WORKS
What an unvented cylinder actually does.
An unvented cylinder stores hot water under mains pressure instead of relying on gravity from a tank in the loft. Four parts do the work.
01
Fed straight off the mains
There is no cold tank in the loft. The cylinder is connected to the incoming mains, so hot water arrives at the tap at the same pressure as the cold. That is why showers feel different on an unvented system.
02
Heated by your boiler, or an immersion
Your boiler heats the water through a coil inside the cylinder. Most also carry an immersion heater as a backup, so you are not cold if the boiler goes down.
03
The expansion vessel takes up the growth
Water expands as it heats. In a sealed system that expansion has nowhere to go, so a vessel absorbs it. If that vessel loses its charge the pressure relief starts weeping, which is the most common unvented fault we get called to.
04
Pressure relief and the discharge pipe
A relief valve, a tundish and a discharge pipe run to a safe outside point. That chain is the whole reason G3 exists, and it is the part a non-qualified installer gets wrong.
What size cylinder do I need?
Sizing is about how much hot water gets drawn at once and how fast it reheats, not about matching whatever is in there now. This is the starting point we work from before looking at your actual setup.
120 litres
1 to 2 people
One bathroom, light use
150 litres
2 to 3 people
One bathroom
180 litres
3 to 4 people
One bathroom and an en suite
210 litres
4 to 5 people
Two bathrooms
250 litres
5 to 6 people
Two or three bathrooms
300 litres
Larger household
Three or more bathrooms, or a bath that fills often
A cylinder that is too big costs you to heat water nobody uses, and one that is too small runs cold halfway through the second shower. We check your incoming mains flow before recommending anything, because an unvented cylinder on weak mains will disappoint you whatever size it is.
Areas covered
Where we work in South Wales
Radiators
Swaps, upgrades and new installs.
Taps and sinks
Kitchens, bathrooms, cylinders.
Underfloor
Laid, tested and commissioned.
New boilers
Fitted for the price we agreed.
Gas safety
CP12 certificates, same day.
Servicing
Annual service, warranty intact.
Radiators
Swaps, upgrades and new installs.
Taps and sinks
Kitchens, bathrooms, cylinders.
Underfloor
Laid, tested and commissioned.
New boilers
Fitted for the price we agreed.
Gas safety
CP12 certificates, same day.
Servicing
Annual service, warranty intact.
All you need to know
Do I legally need a G3 qualified installer for an unvented cylinder?
Yes. Unvented cylinders are covered by Part G3 of the Building Regulations and it is illegal for anyone without the G3 qualification to install one. It is a pressurised vessel, so the discharge and safety arrangements have to be right. We are G3 qualified and we notify Building Control for you.