When it comes to hot water cylinders,  there are so many options available that knowing which one to get can be daunting to say the least......

For example, if you do not wish to install a solar system or a wetback in the future,  you could use a standard hot water cylinder. They are made from mild steel and have a glass liner in them.  However, electricity prices are always increasing (way beyond inflation/CPI) so installing a solar panel is a smart investment either now or in years to come.  The main issue with standard cylinders is that they are not designed to be heated up over 72°C....  From that point it would be better to install a stainless steel (for mains pressure) or a copper cylinder (for low pressure) as they can be heated up to higher temperatures. That will allow you to take advantage of  the higher temperatures of your solar system and store more heat in your cylinder. The other advantage is copper or stainless cylinders last about twice as long before they will need replacing.

Low Pressure V ersus Main Pressure

Most people  install a mains pressure cylinder for just one reason... and that is to have good shower pressure . The other reason is, if for example somebody in your home turns a tap on while you are in the shower, you will usually notice any difference in pressure, or the temperature (your shower turns cold).                                                                                                     

The disadvantage with high pressure is that you will also use a lot more hot water, therefore resulting in a higher power bill. If for example you already have a low pressure cylinder and you are happy with it, but would just like to have a bit more pressure, you could install a small  "hot water booster  pump" instead. That will give you more water flow in your shower , without having to spend a lot of money of upgrading your low pressure system to mains pressure. In addition with a new mains pressure cylinder you may also need a new valve kit and in most instances you will also have to upgrade your bathroom fittings . Booster pumps are available from SolarOne Ltd .

Thinking about having a wetback connected to your hot water cylinder?

Connecting a wetback to your hot water cylinder is a good idea, while you  enjoy the cosy heat from your fireplace, excess heat is used to heat your hot water . To install a wetback to a hot water cylinder you will need a cylinder with a wetback connection . They are specially designed to take the hot water from your wetback/ boiler . The most cost effective way to do that,  is to connect a wetback to a low pressure hot water cylinder. You cannot connect a wetback to a mains pressure cylinder, unless the cylinder has a coil in it (heatexchanger). Cylinders with coils are usually a lot more expensive for that reason, and the installation costs are very high as well. The main reason for that is that the wetback has to be open vented  (like a low pressure system) and there is a lot of extra plumbing involved.

Cylinder Size

Generally speaking , allow about 60-80 litres of hot water per person. While a 180L cylinder in most circumstances is sufficient, when it comes to solar heating, the bigger your cylinder is the more hot water you can store, so you can use that hot water on the not so sunny days. Even if there are only two people living in your home, and you are planing to install a solar system in the future, a 250L hot water cylinder is not to big . If there are 3-4 people in your household a 300 litre is a good option.  Even though a 300 litre cylinder is well a bit on the large side, it doesn't mean you are heating all the 300 litre of water up all the time, you could choose to have a top element in your cylinder and only heat the top of it up.

Replacing a hot water cylinder with a second hand cylinder  ( used cylinder )  

                             
When your hot water cylinders needs replacing, the choice you have is to replace it with a brand new cylinder or a second hand one.
Replacing it with a second hand one is sometimes pretty tempting,, because you can buy a “only 10 year old “ cylinder for 1/4 the price a new hot water cylinder would cost.

Stainless steel cylinders and copper cylinders are usually not sold as "second hand "cylinders Because they do tend to last 20-40 years, and people tend to keep them.

The "second hand" ones that you find are standard (glass lined) cylinders. Standard glass cylinders usually need replacing between 10-20 years.
A cylinder that is 10 years old is well past its life expectancy, as far as most manufacturers are concerned. So why would you want to buy it? 
If a hot water cylinder is more than 6 years old it is not economical due to the plumbing costs of the installation and removing the old one.  Second hand cylinders may look perfect on the outside, but it’s the inside that counts, and there is no way of telling if the glass liner has cracks in it and if the perfect looking hot water cylinder is slowly corroding a way on the inside. It is not worth taking the risk as it’s a bit like buying a  used tyre for your car and hoping it will keep you safe on the roads. A second hand hot water cylinder may not be risky to your life, but it may be risky to your pocket if you found out that you bought a lemon….

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