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Unvented pressurised water cylinders
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Why upgrade your old water cylinder to an unvented pressurised water cylinder?
Installing a low energy consumption hot water cylinder can significantly reduce your energy bill, improve bath filling times, increase shower pressure and increase and free up value space in your airing cupboard or bathroom as they can be installed in lofts, garages and utility rooms. Also, you may have a tank which is to big or to small, heating more water than you need or running out of water because the tank is too small.
Heating hot water can account for over 50% of your energy consumption so choosing the right hot water cylinder can save you £100s per year. We offer a range of low-energy consumption electric hot water cylinders for you or your business.
Our hot water cylinders are incredibly well insulated and have an extremely accurate thermostat which means less temperature variation. Less temperature variation means less energy used. They are also designed to take advantage of economy 7 tariffs & renewable energy sources and are complete silent.
We offer a free consultation to understand your requirements, we can guide you through different options, and answer any questions, a free survey and hassle free installation service. Whether you are a homeowner, landlord or social housing provider sit back and relax with our award-wining installation service.
We are Which Approved Installers and EDF Energy exclusively uses Greenvision for all their high heat retention storage heater installations.
The benefits of unvented water cylinders
Increased water pressure
Invigorating showers and quick filling baths are achieved with pressured hot water cylinders. We can remodel your airing cupboard to create more space.
Energy efficient lower energy bills
Pressure Cylinders have superior insulation and extremely accurate thermostats which means less temperature variation. Less temperature variation means less energy and cheaper bills.
Never run out water, multipe showers running
Lay back and relax and never run out of hot water again. Improve bath filling times and increase shower pressures. Now is the time to install a pressured hot water cylinder and start saving energy
Space saving and can be installed in lofts
A pressured hot water can be installed in lofts, garages utility rooms etc, freeing up valuable space in your airing cupboard and bathroom
Five things to consider when upgrading your water cylinder
Only company with plumbers that hold a G3 certification can install or maintain an unvented cylinder.
As with any major changes to your home it is vital to do plenty of research and talk to the experts about your requirements.
Make sure you know what you want to get out of your new system. Greenvision will be able to offer advice on the best option for your needs and budget.
What type of cylinder should I install?
Think about your type of property and your requirements e.g. if you are in a mid floor flat with no loft access and your cylinder is positioned in the centre of your flat it may be difficult to install an unvented cylinder. A thermal store may be a better option as there is no need for additional pipework. Greenvision can advise on this.
Greenvision will guide you through the minefield of different heating options and answer any questions you may have. We believe knowledge is power and helps you make the right decisions. That's why one of the largest energy companies exclusively use Greenvision Energy for all of their electric heating solutions for their customers.
If you only have one bathroom, with just an electric shower you will only need a small cylinder or undersink heater that heats water at the point of use.
If the have multiple bathrooms and require two showers running at the same time with a drop in water pressure then a accumulator tanks are a good options.
If you are using a shower running off your water cylinder, you need to bear in mind that a pressurised water cylinder can use up to 8-12 litres of water per minute. So a 120L cylinder can be drained very quickly. Greenvision can advise on your best options
If you have economy 7 tariff it is a good idea to have two heating elements on your cylinder. One connect to your economy 7 power supply for cheap low rate electricity and the other elements connect to your on-peak supply for boosting your hot water outside of your economy 7 times.
You might be able to free up valuable space by moving the cylinder into the loft or garage. If your cylinder is located in your bathroom and you are planning to remodel your bathroom it could be a good time to plan ahead.
What are my options when replacing old water cylinders
How does unvented water cylinder work?

An unvented system has no cold water tank, but a sealed hot water cylinder which is fed directly by the cold water mains. An unvented cylinder is kept pressurised from the incoming water supply and is heated by either an immersion heater (a direct model) or by an external heat source such as a boiler or wet solar system (an indirect model).
An unvented cylinder will have pipework connected to it that distributes the hot water to multiple outlets around the house. As soon as a tap or shower is used, the pressure of the incoming cold water drives the hot water in the cylinder towards the open outlet at mains pressure.
Unvented systems are ‘sealed’, so they use an expansion vessel to allow for the expansion of water in the system as it heats up. The expansion vessel is sited either next to or within the boiler or cylinder and can accommodate the increase in pressure by up to 4.5 bar.
What are the benefits of unvented water cylinder?
Increased Water Pressure – Invigorating showers and quick filling baths are achieved with pressured hot water cylinders. We can remodel your airing cupboard to create
- Lower Energy Bills -pressure Cylinders have superior insulation and extremely accurate thermostats which means less temperature variation. Less temperature variation means less energy and cheaper bills.
- Never Run Out Of Hot Water – Improve bath filling times and increase shower pressures. Now is the time to install a pressured hot water cylinder and start saving energy
What is a PowerStore Thermal Store Water Cylinder?
The PowerStore is perfect for modern apartments and all-electric homes, this hot water system gives you the benefits of mains pressure hot water without the need for relief valves and discharge pipes. Designed with modern lifestyles in mind, installation is simple, maintenance is low and the unit is compact.
The hot water store works on the thermal store principle of using a bank of heated water with an efficient internal heat exchanger connected to the mains for fast flowrates for safe power showering and rapid bath filling.
The unit is fitted with a hot water control pack and two 3kw immersion heaters. It is made from stainless steel for long life and has 60mm insulation to meet Part L of the Building Regulations.
What are the benefits of PowerStore thermal store water cylinder?
- Improves bath filling times and Increases shower pressures
- Unrivalled heat retention – minimises heat loss for lower energy consumption and running costs
- Peace of mind – 10-year guarantee.
- Reduced noise levels – this pressured system is completely silent.
What is an under-sink water heater?
Under sink water heaters are Ideal for flats or properties that only have one bathroom with an electric shower and without a bath. If you don’t have a bath your hot water consumption will be low, so there is not a requirement to fit a bulky water tank, that requires you to heat large volume of water you don’t need. Under sink heaters heat water at point of use saving you energy and money.
- Fast heat up time because the tank is right next to the sink water.
- Energy-efficient as you are only heating water when you need it.
- They save you time by not having to wait for hot water to heat up
- Free’s up valuable space in your airing cupboard
Sunamp
Sunamp thermal battery water cylinders can be charged by renewable energy (eg. solar PV) or grid energy and accommodates both on & off-peak tariffs
These thermal batteries are designed for retrofitting existing hot water systems or for use in new build projects.
Their sleek, super-compact design means they look good in any home and free-up valuable storage space.
How does the Sunamp work?
Sunamp thermal batteries are energy-saving thermal stores containing Plentigrade: a high-performance phase change material (PCM) that delivers heating or cooling reliably, safely and efficiently.
The technology has resulted in a uniquely successful formula which is transforming how we use energy and provide heat around the world.
What are the benefits of a Sunamp?
- Compact design – 4 x smaller than an equivalent hot water cylinder
- Improves bath filling times and increases shower pressures
- Unrivalled heat retention – minimises heat loss for lower energy consumption and running costs
- Peace of mind – 10-year guarantee.
- Reduced noise levels – this pressured system is completely silent.
- Instant hot water (without storing water)
- Works with air-source heat pumps, ground-source heat pumps, photovoltaics (PV)
How does Mixergy water cylinder work?

Mixergy electric tanks uses top-up technology. It floats hot water on top of cold. This means you can selectively ‘heat what you need rather than the whole tank. A sensor within the tank ensures you’ll always know how much hot water is available. A specially designed inlet diffuser which keeps hot and cold water volumes separate. This means a Mixergy water tank is up to 20% more efficient than conventional tanks, delivering the hot pressured water, and reducing your energy bills. Works with solar PV and heat pumps.
What are the benefits of Mixergy water cylinder?
- The Mixergy cylinder is up to 20% more efficient than conventional tanks, delivering the hot water you need with less energy. Reducing your energy bill and carbon foot-print.
- Mixergy learns how much hot water you typically use each day, it’s completely in tune with your routine – but won’t waste time and energy heating water you don’t need.
- Pressurised hot-water giving invigorating showers and baths can be filled much more quickly.
The Mixergy app puts you in control of your water tank. You’ll find a wealth of interesting facts about your energy consumption and how to save energy. Or you can sit back and relax and let the self-learning algorithm calculate your water needs for you.
What is a gravity-fed water cylinder (vented)
https://youtu.be/I1QCfsb–Lk
Vented hot water tanks remain the most common type of hot water system found in the UK. Unlike newer unvented tanks, these copper tanks are fed by cold water from a header tank (normally located in the loft) and use gravity to drive the hot water around the home. Cold water in the header tank is linked to the vented hot water cylinder through a vent pipe.
The hot water pressure tends to be governed by the height of the water tank above the tap or shower feed which means that, although the pressure might be excellent on the ground floor of the home, in rooms on upper floors the pressure will be lower.
As a result, many showers in homes with vented hot water tanks use electric pumps to drive the hot water to the shower at increased pressure. Vented hot water cylinders are far less complicated than the pressurised unvented systems so they are much simpler to maintain and install. This makes them a far cheaper option when compared to the unvented system.
More Reasons To Buy Unvented Water Cylinders
Free up valuable space
If your cylinder is located in your bathroom or bedroom or you may have plans to remodel these rooms, you can relocate your new cylinder to a new location (loft or garage etc.)
Much faster heat up time.
Pressured hot water cylinder can produce fast efficient hot water very quickly. So, if you ever run out of hot water you don't have to wait long for a full tank of hot water
Reduced Noise Levels
No more waking up to cold water filling up the water storage cistern. The pressured system is completely silent and sealed, so not at risk of contamination and won’t freeze in winter months.
Hassle Free Installation
Sit back & relax with our award-winning installation service
We are easy to do business with—no lengthy appointments and a quick quote within 24 hours. We’ll never try to pressure you into buying from us. Instead, we give you the information you need to make an informed decision. That’s why one of the largest energy companies in the UK, EDF Energy, trusts Greenvision to install electric heating solutions for their customers.
FAQ's about hot water cylinders
Yes, Greenvision has a range of cylinders that you can control via a smart app.
With this type of cylinder there is no need for a storage tank as water comes straight into the cylinder via the water mains. Mains pressure means gravity feed does not apply, so the cylinder (minus storage tank) can be positioned virtually anywhere at any height, and you get a much more powerful flow than from a vented system. Also, you don’t have to worry about water freezing in a header tank during very cold snaps.
In an unvented installation the system won’t suffer contamination because it is sealed and bypasses areas were impurities could get into the water. With regards to water expansion, the unvented cylinder has either a permanent air bubble infused at the top of the cylinder, or a fitted expansion vessel.
Both vented and unvented hot water cylinders can use either direct or indirect heating systems. With the indirect method the cylinder is heated by a gas boiler or other external source. Hot water passes from the heat source through a copper coil built into the cylinder. In this case it’s a good idea to fit a reserve immersion heater in case of boiler breakdown, so you still have hot water.
The direct method involves one or two heating elements inside the cylinder that heat the water directly. Using the two element option can be very cost effective because it is specifically designed to be used with the Economy 7 tariff – one element for peak day time use and one for off peak where the water is heated cheaply at night and used when needed.
Vented hot water cylinders need a water storage (header) tank to store water piped in from the mains. The tank is usually installed in the loft (or in the highest point in the property) and the system relies on gravity to create a reasonable pressure for the hot water to circulate throughout the property.
Vented cylinders are easier to install than unvented, but they do need a vent pipe to deal with water expansion issues. Households most likely to benefit from vented water cylinders would be properties with an electric shower only, no bath and just one or two people living there.
You should only have an unvented hot water system fitted and serviced by a qualified person holding a current G3 Unvented Qualification. All installations of unvented hot water cylinders have to be notified to Building Control as required by Building Regulations. If your installer is a member of a Competent Persons Scheme, this will happen automatically and you will receive a Building Regulation Compliance certificate.
A hot water cylinder should last for more than 20 years if fitted correctly and to the highest standard. However, the life expectancy of a hot water cylinder can be shortened by water leaks.
They can be installed in almost any location – the garage, upstairs, downstairs, loft or even in a basement. An unvented hot water cylinder needs a safety discharge pipe. Therefore in some basement locations, a sump and pump may be required.
You should consider replacing your hot water cylinder if it is leaking water, but drying at the same time. Leaking water can get worse over time and cause damage. Small leaks can be hard to detect so you should always check for any damp patches surrounding a hot water cylinder. Consult your plumber or call Greenvision Energy if you are unsure about whether your hot water cylinder has a slow water leak.
- If you get constant leaks or breakdowns it could work out cheaper to replace rather than to keep repairing.
- Your new boiler will be much more energy efficient and could pay for itself quite quickly.
- If you have a big family or use lots of water, a new professionally fitted boiler will be sized correctly for your needs, which may not be the case at present.
- If you have an old boiler with a red jacket you will be paying higher energy bills than you need to. You would be better off upgrading to a new cylinder and better tariff. The off peak tariff in conjunction with the two element cylinder could save you lots of money.
- If your water pressure is low and it takes forever to run a bath or the shower is just a dribble, a new unvented hot water cylinder will give amazing improvements.

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