What is a Pressurised Water Tank and Should I Install One?

You may have heard the term ‘Pressurised Hot Water Cylinder’ thrown around when in conversation with you local plumber, but what exactly is one, and more importantly, should you install one. If you haven’t already installed a pressurised water tank, you might be wondering if this is something that could significantly improve your home comfort. There are many benefits that come with installing a pressurised tank that will make a real difference to your home.

Here at GK Plumbing, we specialise in all things plumbing, so we’ve have written this article to help you to fully understand the benefits of installing a pressurised water tank system into your home.

What is a Pressurised Water Tank?

Before discussing the benefits of a pressurised water tank, it makes sense to make sure you are 100% aware of what one is. A pressurised water tank, or a pressurised hot water cylinder, provides the home with pressurised hot water.

Most traditional water tanks are gravity fed, meaning that the water that goes into the cylinder tank is fed from another tank that is located above the cylinder – usually in the attic.

Pressurised tanks, on the other hand, do not require gravity and can produce hot water for all taps around the home without the need of a secondary tank in a higher position. They are the preferred option for flats and new builds with up to 3 floors (ground, 1st floor, 2nd floor).

There are typically two types of pressurised water tanks that are installed into UK homes, unvented cylinders and thermal store cylinder systems.

What is an Unvented Cylinder?

An unvented cylinder is a singular tank (typically manufactured out of copper or steel) that stores hot water that can then be transferred to your hot taps. The unvented cylinder will store cold water which is then heated ready to be distributed into the home. There are two types of unvented cylinder, indirect and direct.

What is an Direct Unvented Cylinder?

A direct unvented cylinder is a tank that uses immersion rods to heat the hot water. The immersion rods use electricity to heat. This is a more expensive method of heating your water. It should only be considered if you use night storage heaters and use an economy 7 energy tariff, or if there is no gas available in your area.

What is an Indirect Unvented Cylinder?

An indirect unvented cylinder is a water tank that has a connection from your boiler to the tank. The boiler will heat the water which is in the tank. The tank is then able to distribute pressurised hot water.

Most unvented systems will have an inlet pipe that sends the hot water through a spiral coil. The coil will transfer the hot water that runs through the pipe to the cold water that is stored within the tank, and thus heats the water in the tank. Indirect systems still have immersion rods in case your boiler breaks down, but the immersion rods can be switched off whilst the boiler heats the water.

Both of these types of cylinders will have an expansion vessel to store hot water when there is too much hot water in the tank. This is needed because hot water expands and as it rises the amount of space that is required for 50L of water, for example, is not enough to store the water once it is heated.

Traditional gravity-fed systems do not require expansion vessels because the tank located in an area above the storage tank acts as an expansion vessel when the water expands.

What is a Thermal Store?

A thermal store is a vented pressurised water tank. Unlike unvented systems where the hot water in the tank is sent to the taps, the thermal store heats water that is already in the tank and then uses the heat from that water in the tank to transfer heat to incoming cold water.

Instead, the system has an inlet pipe that either sends pressurised cold water through a spiral coil within the tank or an alternative system where the cold water passes a thermal plate that transfers the heat to the passing cold water.

The incoming cold water has heat transferred to it from the hot water that is already in the tank. Unlike the unvented system, most thermal stores do require a header tank for refilling the stored water area, but this is significantly smaller than the header tanks required for gravity-fed vented systems.

What is an Direct Thermal Store?

A direct thermal store uses immersion rods to heat the stored water. It uses the exact same transfer method as the indirect – by transferring the heat from the stored water to the incoming cold water. Direct thermal stores should only be installed into homes that are not heated by gas. They are best suited for homeowners with night storage heaters and an economy 7 energy tariff.

What is an Indirect Thermal Store?

An indirect thermal store is a pressurised water tank that heats the stored water using the heat produced from other heat sources including heat pumps, boilers and solar panels. This is the best option for homeowners that heat the house using gas. This system does come with immersion rods in case your other heat sources breakdown.

Benefits of Installing Pressurised Water Tank System?

The obvious answer to this question is that you will benefit from pressurised hot water. This means you can

Install a power shower.
Less chance of tank freezing.
Quicker to fill a bath or basin.

On another note, the main benefits are noticeable when you compare a pressurised system to a vented system.

A huge advantage of the pressurised system is that you will save space. Whereas traditional systems require a large tank in the attic or other areas above the actual tank, pressurised systems do not. This means that you will save space in your attic. As pressurised systems do not require a header tank, the water is stored in one less location, which improves hygiene and also reduces the risk of leaks in the home.

Space Saving
No Large Header Tank
More Hygienic
Less Noisy Compared to Gravity Fed Systems

Should I Install a Pressurised Water Tank?

There is no simple answer to this question and it does depend on a number of factors including

Type of heating system you have
Number of people living in your property

If you live in a property that has a combi-boiler, it is unlikely that you will require a pressurised hot water cylinder unless there is a large number of people living in your property. This is because the combi-boiler already provides pressurised hot water and acts as your hot water cylinder.

However, if you live in a property that does have a large number of occupants, you may wish to install a pressurised hot water cylinder to guarantee all in the property can benefit from the heated water. This would mean that when showering or bathing, the cylinder would provide the hot water until it has run out of heated water, and the combi-boiler would then provide the heated water until the water in the pressurised cylinders has reheated.

I Have A Traditional Boiler. Should I Install A Pressurised Hot Water Cylinder?

If you have a traditional boiler, it is best to continue using your gravity-fed water tank because traditional boilers work best using low pressure. However, if you require pressurised hot water because you plan on installing a power shower, you can install a pressurised hot water cylinder but would require a pressure reducing valve (PRV) to relieve pressure when water is circulating through the pipes.

It is advisable to upgrade your current traditional boiler and install a new combi-boiler if you require pressurised hot water. Combi-boilers have proven to save homeowners money in the long run.

I Have Electric Heaters. Should I Install a Pressurised Hot Water Cylinder?

If you live in an area where gas is available, it is best to install a completely new gas central heating system with a combi-boiler. You will benefit from lower energy bills as gas is significantly cheaper to buy compared electric. However, if you live in an area where gas is unavailable and would prefer to continue using electric heaters to warm your home, it is a good idea to install a pressurised hot water heater, but only if you are unsatisfied with your current gravity fed system or require pressurised hot water for your new shower.

Can GK Plumbing & Heating Install Pressurised Water Heaters?

GK Plumbing & Heating are qualified to install all kinds of boilers and water heating systems.

If you choose to enquire about a pressurised water heater we will be happy to advise you as to whether this is the best option for your requirements. If it turns out that there is a better option for you we will happily discuss that alternative option with you. We are also happy to install your original option so long as it is safe and legal to do so.

Our services are available throughout the whole of Buckinghamshire, and we have designated plumbers located in Aylesbury, High Wycombe, Beaconsfield, Leighton Buzzard, Milton Keynes and more areas throughout Buckinghamshire.

Get in Touch

If you are ready to install a pressurised hot water system, please contact us today. You can send a message directly through the website. Alternatively, you can call us to discuss your requirements.

See the areas we cover below!

What is a Pressurised Hot Water Cylinder and Should I Install one?

What is a Pressurised Water Tank?