Hot Water Cylinders

Hot water storage cylinders are the most common form of hot water supply in New Zealand. Properties built before 1980 had a low-pressure cylinder that was controlled by a supply tank in the ceiling or later a pressure reducing valve. Most of the new residential construction have mains pressure cylinders.

If your property still uses a low pressure system, there is probably insufficient pressure to run a majority of modern bathroom fittings.

If you are planning on a renovation, it would be advisable to look at getting the hot water system converted to a mains pressure– there are numerous options available. The pipework and fittings should also be checked for their ability to cope with the additional pressure, and it may be necessary to upgrade these as well.

Cylinder Sizing

The hot water storage cylinder should be sized to cope with the maximum/peak water demand, because if it is sized too large that will just increase the running costs. The size of the cylinder will mainly depend on the number of people living in the property. The average hot water consumption is 40–60 litres per day per person.

Hot water cylinder thermostat settings

Hot water from a cylinder needs to be heated to a minimum temperature of 60°C. This temperature is hot enough to kill harmful bacteria that can grow in the cylinder, such as Legionella. Legionella is a common bacteria found in water systems that have not been properly heated and can cause serve illness. The optimum setting for a water storage heater is between 60 and 65°C to avoid over heating and wasting energy and money.

Hot Water Cylinder Tempering

Tempering heated water

The Building Code requires hot water to be delivered at a temperature that avoids the likelihood of scalding. As water heated to 60°C or more can cause serious burns, water must be tempered before it is delivered to sanitary outlets (basins, baths and showers etc.).

Acceptable Solution G12/AS1 sets maximum temperatures for water delivered to sanitary fixtures. For most buildings the maximum temperature of outlets is set at 55°C.The limits are lower for organisations such as hospitals and schools (Building Performance G12 Water Supplies).

Higher temperatures of around 55°C to 65°C are acceptable for kitchen sinks and laundries.

Hot water cylinder and pipe insulation

Hot water cylinders should be insulated along with the first meter of hot water pipe off the cylinder. This reduces the heat loss and keeps the heated water warm, lessening the energy (and cost) required to run the unit. Modern cylinders are designed with insulating material, while older cylinders (pre-2002) are likely to be poorly insulated and need wrapping.

Hot Water Restraints

Hot water cylinders when full have a significant weight to them and due to their tall narrow construction make them unstable during earthquakes. As result it is a legal requirement that all cylinders are adequately strapped in place to prevent falling as a result of any movement.

If you are looking to upgrade your hot water cylinder or are after a Christchurch Plumber then get in touch with us today.

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