An unvented cylinder is connected directly to the mains water supply. It uses electricity or gas to heat water to a pre-set temperature. The act of heating water causes it to expand, which creates pressure within the cylinder. That pressure pushes the water outward throughout your home's pipes.
What You Need to Do. Under Building Regulations, it is necessary to notify Local Authority Building Control (LABC) of the installation of both unvented and vented hot water cylinders. Contact Gas Safe Register to confirm you have a Hot Water qualification. The certification body does not inform GSR for you.
Connected directly to your mains water system, unvented cylinders ensure copious amounts of stored hot water is available on demand and they operate at mains pressure to offer much higher flow rates. This allows you to enjoy improved shower and bath performance all year round!
The main difference between a vented and unvented water storage cylinder is that an unvented hot water cylinder takes its water supply directly from the mains. You can get hot water out of an unvented cylinder at a much better pressure than a traditional vented cylinder as it is pressurised.
Operating Pressure
For typical domestic systems a minimum pressure of 1.5 bar (150 Kpa) and 20 litres/min water flow rate is required. If the water pressure is too low to meet the required operating pressure for the unvented cylinder then water can be fed from a low level cold water storage cistern/tank.Is it cheaper to have my hot water on all the time? No, it's almost always cheaper to have your hot water on when you need it, as a full tank of hot water will always lose heat and need topping up by the boiler. Normally it takes around 30-45 minutes to heat a tank of hot water.
What
size hot water cylinder you need. Whether you need
a vented or
unvented cylinder installation.
What Size Cylinder Do You Need?
| Property Size | Bathrooms | Cylinder Size |
|---|
| 2 Bedrooms | 1 | 150-180L |
| 3 Bedrooms | 1 or 2 | 180-210L |
| 4 Bedrooms | 2 | 210-300L |
| 5 Bedrooms or more | 2 | 300L or bigger |
Unvented hot water cylinders store water from the mains water supply. The water is heated either with heat from a boiler or using other electrical heating elements. This provides high pressure hot water supplies to feeding outlets. The increased pressure helps deliver better quality showers without the need for pumps.
British Plumbing Employers Council
For a Mains (Unvented) 'High Pressure System' a booster pump and/or pressure vessels can be installed directly in line with the rising cold water mains supply, boosting water pressure and flow to the entire property, including the combination boiler or pressurised hot water cylinder system.
What Size of Hot Water Cylinder Do I Need?
| Installation | Indirect Hot Water Cylinders | Direct Hot Water Cylinders |
|---|
| 2 Bedroom + Bath/Shower | 150 | 180 |
| 3 Bedroom + 2 Baths/Shower | 180 | 210 |
| 4 Bedroom + 2 Baths/Shower | 210/250 | 250/300 |
| Larger Properties | 300+ | 300+ |
With repeated use, the cylinder can wear out and need replacing. Ignition cylinders, also called ignition cylinder locks, can cost anywhere from $10-$700. More often than not, though, the cost will range between $70 and $250 for the parts and about $70 for the labor.
Can I use Worcester unvented cylinders on a vented system? Yes you can. You just won't fit the expansion vessel and the inlet control group.
How long do cylinders last? Life expectancy of modern copper or stainless steel cylinders is 20–40 years, but mains pressure glass-lined steel is shorter at 12–20 years.
— The majority of water heaters last between eight and ten years. While ten is the age at which heater replacement is generally recommended, the actual need to replace a heater could arise before or after this timeline.
As water is heated its density will decrease requiring more space and creating more pressure. If this pressure is not managed properly your hot water cylinder could/will explode or “burst” once it reaches its maximum rated manufacturing pressure limit.
HomeCare One is the most basic level of protection that British Gas offer as it protects your gas boiler, its controls, your thermostat and programmer. HomeCare One doesn't cover repairs to your wider central heating system such as your radiators or hot water cylinder.
Indirect Unvented Cylinders
Indirect Cylinders rely on external appliances to apply the necessary heat to the cylinder – this in turn generates the hot water that is stored, or also used as a backup if the main heat source fails.The good news is, it's actually pretty straightforward to switch to a system boiler with unvented cylinder, as it should be able to go in the same space as your old combi. You must also be able to supply hot and cold water pipes to the cylinder.
Unlike a direct cylinder, an indirect hot water cylinder has nothing inside to heat the water. The boiler feeds the hot water into the cylinder. Usually, the indirect cylinder will have an internal coil which sits in the indirect hot water cylinder to heat the water as it passes through.
A Primatic cylinder or a self-priming cylinder, is a type of indirect hot water cylinder in which the water for the central heating is separated from the domestic hot water by an air lock inside the heat exchanger.
What Are The Components Of A Hot Water Cylinder? The Storage Tank. Modern mains pressure hot water storage tanks will usually have a steel inner cylinder which is lined with glass or vitreous enamel, insulation and a steel outer lining. Depending on their age low pressure tanks may have a copper lining.
