The Different Types of Hot Water Cylinders in NZ

The Different Types of Hot Water Cylinders in NZ

Although we use appliances and taps every day, we very rarely think about where the liquid is coming from, and what type of hot water cylinder in NZ we have in place. However, there are several different options for you to choose from, each offering pros and cons. So if you aren’t sure what system you are currently using, or what you should upgrade to, keep reading.


Low Pressure: Open Vented

One of the most common types of hot water cylinders in NZ is the low pressure, open vented system. These work by storing cold liquid in, what’s known as, a header tank. A header tank can be found at a higher level than the storage hot water cylinder in NZ; gravity is then used to help the liquid move to the bottom of the system. It’s common knowledge that heat rises, so as the liquid warms up, it moves to the top of the tank where it can be drawn upon whenever an appliance or tap is turned on. Providing the stored water is higher up than all of the outlets, the water will be pushed through the outlets. However, one disadvantage of this type of system, is that the pressure is not as firm as it is with other options, despite this, the pressure of both warm and cold liquid will come out evenly. Unfortunately, though, it does take some time for the liquid to heat up, so the delivery of warm liquid can be slower than other methods. But, if you can deal with this, it is a cheap and easy option to install and maintain, and it is also relatively quiet.

Low Pressure: Pressure Reducing

This hot water cylinder in NZ option is fairly similar to the open vented system mentioned above. Pressure reducing systems, however, use a valve to reduce the high pressure from the mains supply down to a head. This is able to be maintained inside the vent pipe. This is considered as an older system, and unless you currently have one in your home, would not be installed today, this is mainly due to it’s poor performance in comparison to newer alternatives. One main issue with low pressure, pressure reducing options is that it is an unequal pressure system. Basically, it will supply low pressure hot water and high pressure cold water; this can make it hard to get a balanced flow to the shower. It is often recommended that you consider upgrading your system if you currently have a pressure reducing one. There are so many other options that will make your life much easier.

Mains Pressure: Unvented

These hot water cylinders in NZ use the mains pressure to supply liquid to all outlets. As it uses mains pressure, both warm and cold liquid will be released from taps and appliances at the same pressure. This works by using an expansion vessel that allows the heated liquid to expand. However, it is important that all systems of this design have a pressure relief valve in case the expansion tank fails. These pressure relief valves also need to be both temperature and pressure operated to protect the rest of the system in the event of a dual failure. Although this option is one of the more expensive to install and maintain, it is the most effective system for ensuring that both warm and cold liquid is distributed at the same pressure. Furthermore, the use of mains pressure ensures that you will receive high pressure warm liquid. You will also receive quick warm liquid delivery, meaning you won’t have to wait for it to heat up.


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