Hot water cylinders are used in many residential and commercial buildings to store hot water that can be delivered to outlets throughout the property via regular hot water pipes.
The hot water can be used for as long as water remains in the tank, reliably supplying households with both shower, bath and tap water.
What Types Of Hot Water Cylinders Are There?
Similar to boilers, there are a variety of different types of hot water cylinders available and the one that is suitable for you will depend on a variety of factors. This includes things like your current hot water demands and the type of boiler you use.
There are two main types of hot water systems – unvented and vented cylinders, which is determined by the way the water enters the cylinder. Once heated, the water rises and is then distributed through your property, this is then gradually replaced by fresh cold water at the bottom, ready to be reheated.
What Is An Unvented Cylinder?
An unvented cylinder is hooked up directly to the mains water supply, meaning it is a high-pressure system, with a strong water flow. For this reason, they do not require a separate cold-water tank and they can also be connected to existing heating systems pipework, allowing them to be installed almost anywhere.
Typically, unvented cylinders are made from stainless steel, which tends to retain heat for longer than other metals such as copper.
What Is A Vented Cylinder?
This is a cylinder that is supplied with cold water from a cold-water tank stored in the loft. This means water is fed into the cylinder with the help of gravity via a vented pipe which is then heated in the same way and fed to the water outlets via the pipework.
The vent pipe allows the water to expand as it enters the tank and enables any remaining water to be condensed safely into the cold tank.
Since this system relies on gravity to supply water to the tank, the cylinder has to be located directly beneath the cold-water tank.
Normally, vented cylinders are made from grade 3 coppers and are usually used in conjunction with a conventional system.
Direct vs. Indirect Cylinders
Another distinction is the water heating method that is employed, which can either be direct or indirect.
A direct cylinder utilises an internal component to heat the water, such as an element or immersion heater. Since it is not heated by an external source, it uses electrical power only. The hot water is then released from the top to the property’s pipework.
An indirect cylinder uses an external source to heat the water, such as a boiler. As stated in this post about the types of Worcester Bosch Boilers “The water is heated via a heat exchanger and then fed into the tank where it is stored. Hot water is replenished at a much faster rate and they are available in both vented and unvented versions”.
Immersion heaters can still be paired with indirect cylinders as a backup option e.g. if a gas boiler breaks down or temporarily loses its fuel supply.
Which Type Of Cylinder Is Right For You And Your Property?
When deciding on what type of cylinder is right for you i.e. vented or unvented, here are some factors to consider:
Vented cylinders are more appropriate for homes with older heating systems that cannot handle the high pressure of mains water. Installation costs also tend to be lower, as do the upfront costs of the cylinder itself.
On the other hand, unvented cylinders do not require a cold-water storage tank and so do not require as much space to install and where they can be installed is more flexible. Since they are connected to the mains, they also tend to provide much more powerful water flow.
With that said, it is worth noting that a major advantage of vented cylinders is that they can continue to be used, even if you lose access to the mains water supply.
It is also important to consider your current heating system, for example, its age. If it is an old system, it may not be able to handle the high pressure from the mains, in which case a vented cylinder would be preferred.
Similarly, if your mains water pressure is not sufficient enough, it does not make sense to install an unvented cylinder that relies on high pressure. It is still possible, but you may need to enhance the pressure by installing a pump.
What Size Cylinder Do You Need?
Selecting the right size cylinder for your home is an essential part of the process, you want it to be large enough to meet the demands of your household, but also small enough so that you are not wasting an unnecessary amount of energy and money.
Some people become concerned about storage cylinder size, thinking that if they choose one that is too small they will run out of hot water during use, but this shouldn’t be the case if you select the right size cylinder.
Both types of cylinders – vented and unvented are available in a variety of sizes. They start from around 60 litres hot water capacity and go all the way up to 300 litres.
How Do You Calculate What Size Cylinder You Need?
As you may expect, there is no simple way to determine the cylinder size you require. Instead, the general rule of thumb is that you ought to have up to 45 litres for each member of the household.
For example, the typical UK household with 4 occupants will require a hot water cylinder with a 200-litre capacity. Although, bear in mind that the exact size you need will vary depending on your personal water use and that of the other occupants.