Types of Hot Water Systems Available
There are two main types of hot water systems - Storage water heaters and continuous flow water heaters, which are sometimes known as instantaneous, water heaters.
With storage water heaters, water is heated and stored in an insulated tank ready for use throughout the day. This type of heater operates most economically on solar energy, natural gas, or off-peak electricity. They can also run on LPG, peak electricity or solid fuels such as wood or briquettes. Storage water heaters are available as ‘mains pressure’ or ‘constant pressure’. ‘Mains pressure’ means hot water is delivered at a similar pressure and flow rate as the cold water, and more than one tap or appliance can be turned on without affecting the supply pressure. ‘Constant pressure’ hot water is delivered at lower pressure than mains pressure. Storage water heaters are normally located at ground level and can be installed either inside or outside your home.
Continuous flow, or instantaneous, water heaters, heat water as it is required, and therefore don’t require a storage tank. As water is heated ‘instantaneously’, they cannot run out of hot water. These types of heaters are smaller than storage systems, and can be installed internally or externally, usually mounted on a wall or in a cupboard. They are connected to the mains water supply, and deliver hot water at a slightly reduced pressure. Standard units can generally deliver adequate hot water to one or two taps or appliances at the one time. High powered, high efficiency units are also available, which can serve larger households. Some units have electronic remote controls for temperature control from inside the house. Most operate economically on natural gas, but can also use LPG and day rate electricity.
When choosing a hot water system, consider the size of your family, the purchase and installation price, the unit’s efficiency and running costs, and the life expectancy of the unit.
How energy efficient are they?
Hot water accounts for around one quarter of the average household’s energy costs so choosing the right fuel to heat your hot water can make a significant difference to running costs. The most common fuels for hot water systems are off-peak electricity, for storage units only, and natural gas. Other fuels are solar energy, LPG, peak-time electricity, heat pumps, and solid fuels, such as wood, briquettes, and coal. For similar sized households, both off-peak electricity and natural gas systems cost approximately the same to buy and run. Natural gas can be used in storage and continuous flow hot water systems, and internal and external models are available.
Check the systems energy efficiency rating...the more stars, the more energy efficiency. Off-peak electricity is only available for use in hot water storage systems of 160 liters capacity or more. Water is heated over night, during the off-peak period, to provide adequate hot water for your daily usage. If the hot water runs out, water can be reheated automatically on the off-peak tariff, using a 24-hour off-peak boost. Off-peak electricity is not available for continuous flow systems, and models are available internally and externally.
Solar energy is another efficient fuel alternative. This system is generally the cheapest to run and is the most beneficial to the environment. All solar energy systems come with a gas, off-peak electric or solid fuel booster to supply adequate hot water during periods of low sunshine. They are generally located on the roof of a home, with a storage tank connected to the solar connectors. Mains pressure and constant pressure systems are available, and the storage tank can be located at ground level with some systems.
LPG is another common fuel. It is generally used in areas where natural gas is not available. Running costs average around one and a half to two times more expensive then natural gas or off-peak electricity. Again, and in all cases, look for the Energy Rating Label with the highest number of stars.
Maintaining and Cleaning Your Hot Water Heating System
The life of any hot water heating system is determined by many factors. It is recommended that hot water systems be cleaned at least once a year, to get rid of mineral deposits that collect inside the unit and its pipes. Those deposits of iron and other minerals will eventually hinder the efficiency of your hot water system.
Tank corrosion is the main cause of hot water heating system failure. Stainless steel and copper tanks tend to have a longer life span than those systems lined with vitreous enamel or glass.
Continuous flow heaters should have a relatively long life provided they are well maintained. Major components such as heat exchangers can be replaced without having to purchase a complete new system.
Properly maintained solar collectors should outlast the life of the storage tank. When the tank needs replacing, the existing collectors can be connected to the new tank. Cleaning your unit, whether it is gas or electric, requires a flushing.
Even though continuous flow or instantant hot water systems do not have a storage tank, they often develop a build up of lime scale. This usually requires an acid treatment when cleaning. Check to see that your warranty is still valid. Then leave it to the professionals and call a licensed plumber when you plan to clean your hot water system.
Have a Professional Install It For You
The installation and use of your hot water system has a substantial influence on the running costs and life span of your system. For high efficiency, have your system installed by a licensed plumber and electrical contractor. The optimum water temperature for storage hot water systems is between 60 and 65 degrees Celsius.
Have your system installed as close as possible to all points of hot water use, such as the bathroom, kitchen, and laundry. If this is not possible, locate your system to where small, regular amounts of hot water are drawn off...usually the kitchen. Keep pipe runs as short as possible to minimize heat loss from pipes. It’s a good idea to insulate your hot water pipes, especially the first two meters leading from the hot water system. Closed cell rubber insulation is recommended and remember, keep this dry.
Consider installing a timer on peak rate electricity storage units, and low flow showerheads to reduce the amount of hot and cold water delivered. For solar hot water systems, install solar collectors to face true north. For constant pressure storage tanks boosted by solid fuel, such as wood, heaters, install them directly above this heater to make full use of the natural rise of the heated water to supply the tank.
Bear in mind that warranties offered for hot water services range from 5-10 years for glass or enamel lined tanks, 7-10 years for stainless steel tanks, 7 years for copper tanks and around 10 years for heat exchangers of continuous flow heaters.
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