If you just need enough hot water for occasional hand washing at a single sink, an instant water heater is a good place to start. These are small electrically powered units that heat water 'instantly' as it flows through the product. Instant water heaters have the advantages of being compact, relatively cheap to buy and easy to install above a sink but they can only serve one sink and they can normally only heat water relatively slowly.With these products the temperature of the outlet water depends on the water flow rate; the faster the flow rate the less the temperature rise will be and vice versa. This means that you might have to accept quite a slow flow rate when the incoming water is very cold, for example in winter. However an instant water heater will never run out of hot water and will not use energy when it is not being used.
If your typical application is dish washing at a single sink, you will need larger quantities of hot water at a time than an instant water heater can easily supply. In this case a storage water heater is likely to be best. These pre-heat a quantity of water in a tank for later draw-off. Over-sink storage water heaters are the most economical and easiest to install. These are mounted over a sink, and are supplied complete with a valve and a spout. However you are usually limited to locating them above a sink and you can also only serve one sink at a time.
If you want to serve multiple sinks or wish to locate the heater out-of-sight, e.g. beneath a sink, you will need a mains pressure storage water heater (sometimes called an unvented water heater). These heaters let you install the heater more or less anywhere but because the tank pressurised at the incoming cold mains pressure you will need to fit a safety valve and possibly other accessories too if there is a cold water drinking supply nearby or if the incoming water pressure is unusually high. This makes installation a little more complex and the heaters are more expensive but overall we believe these heaters offer a much better solution than either instant or oversink water heaters and they are our best selling water heating products.
To provide hot water for 4 or more sinks or for a shower or a bath t he best solution is a large mains pressure storage unit. These can be located flexibly and give high pressure for showers without needing a pump or a header tank in the loft. A small flat would require a unit of a least 90 Litres capacity and a 3-4 bedroom house at least 150L. Capacities of approximately 100L or more can usually be heated by a central heating boiler as well as electrically. Use of a central heating boiler is termed 'indirect' in contrast to electric heating which is termed 'direct'. Indirect heating is generally recommended in the long term as running costs will be lower, although the initial capital cost would be a higher.
Mains pressure units do need various safety valves to be fitted. Everything required is included with the heaters, but plumbing experience is very valuable for installation.
You should note that traditional low pressure copper cylinders are an option too. We do not sell these as they do not offer good water pressure, but they are relatively cheap and simple to fit.
Water for drinks needs to be heated to nearly 100 degs C and special products are designed for this purpose. Your choice comes down to traditional manual catering urns and automatic fill wall mounted or counter-top units. Traditional manual units are relatively inexpensive but have to be re-filled by hand and boiling water is unavailable as they re-heat. Gas heated versions are also available. Automatic units are connected directly to the water mains and provide near boiling water for hot drinks on demand without requiring any intervention but are significantly more expensive. Please note that the information in this guide is intended to provide high level information of a generic nature and should not be taken to imply the suitability of a specific product in a specific situation. Please also note that all products must be installed by a competent person in accordance with the manufacturers' instructions and appropriate regulations.
If you need further information please do not hesitate to contact us. We will do our very best to help you in your exact situation. We have many years of experience with water heating products and have access to a wider range of products than we can show on our website so if you have an unusual requirement please contact us with the details and we will to our best to help.