Hot water cylinders can still be found in most homes across the UK, despite the growing popularity of combi boilers. Hot water cylinders store large amounts of hot water so it is available on demand for baths, showers and use in the kitchen for washing up. The correct hot water cylinder for your home will depend largely on how much hot water you require throughout the day. Hot water cylinders and immersion heaters are usually kept in an airing cupboard or loft, however there are unvented type cylinders that can be placed almost anywhere in the home.
There are many types of cylinder available such as Mains Pressure Unvented Cylinders, Vented, Direct, Indirect, Thermal Store and Solar Cylinders. This wide range of hot water cylinders comes from manufacturers including Gledhill, Santon, Vaillant, Heatrae Sadia, OSO, Glow Worm and Worcester. Unvented cylinders work off mains pressure using the water main pressurisation to move the domestic hot water around the property so do not require a header tank in the loft.
Unvented cylinders are usually manufactured out of stainless steel and offer higher hot water flow rates so are ideal for providing higher water pressure for showers. Vented cylinders use a header tank rather than mains pressure, so are usually situated within the loft area and rely on gravity to pass the water through the pipes to your heating/hot water system.
Vented cylinders are usually manufactured out of copper. Direct cylinders are heated via an internal element, usually an immersion heater. Once the water has been heated it is supplied to the required outlet, this type of cylinder is available in both vented and unvented models. Indirect Cylinders are heated via an external heat source, usually a boiler which heats the water inside the cylinder using an internal coil which transfers the heat obtained to the water inside the cylinder.
However, indirect cylinders can also be fitted with immersion heaters as a supplementary heat source. Solar cylinders are the new kid on the block, they are specially designed for modern solar heating installations. A mixture of water and a special Glycol liquid is circulated through pipework then returned to the cylinder where the heat is transferred to the stored water via an internal coil. Often solar cylinders have an alternative heat source in the form of an internal immersion heater for times when solar radiation is insufficient for the hot water needs.
Plumbers are trained to be competent working with a wide variety of heating and water systems, so any qualified plumber should be more than capable of installing or maintaining any hot water cylinders. Be aware however that immersion heaters use mains power to heat water so you may also require the services of an electrician for some jobs.
When hiring a plumber or electrician, the same rules apply as with choosing any tradesman, namely, choose by personal recommendation if possible, if not get at least 3 quotes and ensure all tradesman are qualified and competent with the right experience. Finally, check they carry sufficient liability insurance and never pay in full up front!