Vented Hot Water Cylinders
A vented cylinder is a copper water tank, typically found in an upstairs airing cupboard, that supplies your house with hot water. It is accompanied by a cold-water storage tank, located above it, which usually supplies water to the cylinder and to your cold-water outlets. Vented cylinders rely on gravity, with the cold water from the higher tank pushing the heated water in the lower cylinder to your taps. They usually deliver poor water pressure to the floor they are situated on unless a secondary pump is fitted to increase the flow to the hot water outlets.
Unvented Hot Water Cylinders
Unvented hot water cylinders have grown in popularity over the years due to their consistent and improved flow rates over vented cylinders. Unvented cylinders rely on mains pressured water rather than a storage tank, thus saving a great deal of space and delivering excellent flow rates to hot taps. Unvented hot water cylinders are usually made from stainless steel as opposed to the copper bodies of older tanks, making them cheaper to manufacture and easier to install. Stainless steel is also far more effective at withstanding high pressures and temperatures.
A vented or unvented cylinder can be of the direct or indirect variety. Direct cylinders are heated via electrical immersion heaters fitted into the cylinder and do not require a boiler to run. Indirect cylinders require central heating boilers to heat the water stored in the cylinder. The heat from the boiler is pumped through a coil inside the cylinder which indirectly heats the water stored in the tank. Contrary to popular belief, these two water sources are separate and the water inside your system/conventional boiler is not the same water that comes out of your taps.
How Do They Work?
Vented cylinders are an antiquated method of storing and providing hot water. They work primarily via gravity and are sometimes referred to as “gravity cylinders”. A cold-water storage tank located above the cylinder forces water into the bottom of the hot water cylinder and out of the connected outlets (taps, showers, etc.). Vented cylinders have a vent pipe which terminates above the height of the storage tank in the loft. When the water in the cylinder is heated it expands and is accommodated by the vent/expansion pipe. The water in the cylinder is either heated directly via immersion heaters or indirectly via a boiler.
Unvented cylinders heat their water in the same way but are supplied by mains pressured water rather than by a cold-water storage tank. Unvented hot water cylinders are pressurised and rely on an expansion vessel or air bubble to accommodate expansion rather than a vent pipe, hence the name. They deliver much better pressure than vented cylinders due to being fed by mains pressure cold water.
Why Upgrade My Hot Water Cylinder?
Unvented hot water cylinders are the perfect choice for domestic properties with two or more bathrooms. They can be installed in a basement, airing cupboard, or loft, which makes them ideal for those with limited space options.
Unlike combi boilers, which struggle to maintain flow rates when multiple hot taps are in use, the pressure behind an unvented cylinder enables them to cope with running multiple hot water outlets at the same time with little discernible drop in flow rates. This makes them a better choice for homes in multiple occupation.
Should I Upgrade My Hot Water Cylinder?
If you have an old hot water tank that isn’t performing as well as it used to or even if you are just simply tired of sub-par hot water pressure, then it might be time to upgrade to an unvented hot water cylinder. If your cylinder is leaking, then it is advisable to consider having it replaced.
Regulations brought into place in 2013 stipulate that cylinders must be manufactured to the correct standard and be properly insulated. Cylinders manufactured before 2013 may not be as energy efficient as modern cylinders that comply with Part L of the building regulations. It is still safe to continue using them, but they will not be as economical.
If you are thinking of going ahead with a boiler or heating system upgrade, then it is a good idea to have your cylinder replaced at the same time to maximise on energy efficiency.
What Should I Consider Before Installing an Unvented Hot Water Cylinder?
Unvented cylinders are only as good as your incoming mains pressure, and this is the essential factor to take into consideration when installing an unvented cylinder. As with combination boilers, unvented cylinders are supplied by mains pressured water and have a minimum recommended operating pressure and flow rate in order to function correctly. Most manufacturers recommend a minimum mains water pressure of 1.5bar and a minimum flow rate of 20 litres per minute. We carry out flow rate and pressure checks as part of our free quotation service to assure your system falls within these guidelines.
Space is also a factor to consider. Hot water cylinders typically require a large cupboard to be housed in and must be adequately supported. Indirect cylinders installed alongside a system boiler also require a fair amount of pipework and external components. If space is an issue, it might be worth considering a combination boiler instead.
Upgrading from a gravity-fed vented cylinder to a mains pressured unvented cylinder can also put existing pipework and fittings under stress from the increase in pressure. This can sometimes affect existing toilets and taps and can, in rare circumstances, cause pipework joints to leak. We always highlight potential issues and risks before carrying out a hot water cylinder upgrade.
Unvented hot water cylinders can be dangerous if installed incorrectly. Always check that your installer is qualified to carry out the installation and registration of unvented hot water cylinders. Unvented hot water cylinders are covered by Part G of the building regulations and installers must hold the correct qualifications in order to legally install them. At ASP Plumbing and Heating Services, our installers are G3 qualified and have extensive knowledge and experience of safely installing and servicing unvented hot water cylinders.
How Much Does A New Hot Water Cylinder Cost?
The cost of a new hot water cylinder installation can vary depending on the type, size, and brand of cylinder. We do not display the cost of hot water cylinder installations in our Prices section, but you can expect to pay anywhere between £1000 – £3000 for a hot water cylinder supply and installation. ASP Plumbing and Heating Services offer a free quotation service for all installations, please get in touch via our contact form or by calling 020 3858 0277.