A Comprehensive Guide to Hot Water Cylinders

unvented hot water cylinders with external heat source pump

In our pursuit of providing you with the most informative and comprehensive guide to hot water cylinders, we understand that having access to reliable and consistent hot water is an essential aspect of modern living. Whether it’s for your daily showers, laundry, or dishwashing, a well-functioning hot water system is indispensable. In this guide, we’ll delve into every aspect of hot water cylinders, helping you make informed decisions about this crucial component of your home.

Hot water cylinders are essential components of a domestic heating system that provide hot water to taps and showers. They are made from stainless steel and are available in various types, each suited to different needs and preferences.

Understanding Hot Water Cylinders

Hot water cylinders, often referred to as hot water tanks, are the heart of any domestic hot water system. They store and distribute hot water throughout your home as and when you need it. These indirect hot water cylinders come in various types, and choosing the right one for your needs is essential for an efficient hot water supply.

What is a hot water cylinder?

A hot water cylinder is a tank that stores heated water for later use. It is typically located in a loft or airing cupboard, and it is connected to the system boiler and the cold supply. The boiler heats the water in the water is heated in the cylinder, and then the hot water is drawn off from the top of the tank as needed.

Types of Hot Water Cylinders

Vented Hot Water Cylinder:

Vented cylinders are the traditional choice, and they rely on a cold water tank located in the loft. This cold water is fed to the hot water cylinder, where it is heated by either an immersion heater or a boiler. Vented cylinders are known for their simplicity and reliability.

Unvented hot water cylinders are pressurized to mains water pressure. This means that they can deliver high-pressure hot water to taps and showers, even if the boiler is not running. Unvented hot water cylinders are typically larger than vented cylinders and can store more hot water.

Unvented Cylinder:

Unvented, on the other hand, does not require a cold water tank in the loft. They are directly connected to the mains water supply, allowing for higher water pressure and faster heating. This type is becoming increasingly popular for its efficiency and space-saving benefits.

Vented hot water cylinders are not pressurized. They are open to the atmosphere, which means that the water pressure is limited by the height of the cylinder. Vented direct hot water cylinders are typically smaller than unvented tanks and can store less hot water.

our engineer install a direct hot water cylinder and a cold water storage tank

Choosing the right hot water cylinder

When choosing a hot water cylinder, there are a few factors to consider:

The size of your household: The size of your household will determine how much hot water you need. If you have a large household, you will need a larger cylinder.

Your hot water needs: If you have a lot of showers or baths, you will need a cylinder that can store more hot water.

Your budget: Hot water cylinders can range in price from a few hundred pounds to several thousand pounds. It is important to set a budget before you start shopping.

Sizing Your Hot Water Cylinder

Selecting the right size of hot water cylinder is crucial to ensure a constant supply of hot water without unnecessary energy wastage. To determine the appropriate size for your household, consider factors such as the number of bathrooms, the frequency of hot water usage, and the type of cylinder you have. It’s always advisable to consult a professional to calculate the exact size you need.

unvented hot water cylinder installation in North London

Benefits of using a hot water cylinder

There are several benefits to using a hot water cylinder:

Convenience: Hot water cylinders provide a convenient source of hot water on demand. You don’t have to wait for the water to heat up before you can use it.

Energy efficiency: Hot water cylinders can help the heat source save energy by storing hot water for later use. This means that the boiler doesn’t have to heat the water from scratch every time you need it.

Comfort: Hot water cylinders provide a consistent supply of hot water, which means that you can enjoy a comfortable shower or bath even if other people in your household are using hot water at the same time.

Upgrading your hot water cylinder can bring several benefits to your home and lifestyle. Here are some compelling reasons to consider:

1. Improved Energy Efficiency

Modern hot water cylinders are designed with energy efficiency in mind. Upgrading to a newer model can lead to significant savings on your energy bills. With improved insulation and better heat retention, you’ll use less energy to keep your water hot.

2. Consistent Water Pressure

Unvented cylinders, in particular, provide better water pressure compared to vented systems. This means you can enjoy powerful showers and fill your bathtub faster, enhancing your overall bathing experience.

3. Space Saving

Unvented cylinders, due to their direct connection to and directly from the mains water supply, eliminate the need for a cold water tank in your loft. This frees up valuable space that can be used for storage or even additional living areas.

4. Reduced Maintenance

Newer hot water cylinders often come with warranties and require less maintenance. This means fewer headaches and expenses when it comes to repairs and replacements.

we install unvented hot water cylinders with a central heating boiler

Installation and Maintenance

To maintain your cylinder in good condition, it is important to have it serviced regularly by a qualified plumber. The plumber will check the cylinder for any leaks or damage, and they will also flush the cylinder to remove any sediment.

Proper installation and regular maintenance are vital for the longevity and performance of your cylinder.


Installing a hot water cylinder should always be done by a qualified professional. They will ensure that the system is correctly connected to your plumbing and central heating system, adhering to all safety standards and regulations.


Regular maintenance is essential to keep your hot water cylinder running smoothly. This includes inspecting and testing safety valves, checking for leaks, and flushing the system to remove sediment buildup. It’s recommended to schedule an annual service by a certified technician.


Hot water cylinders are an essential component of a domestic heating system. They provide a convenient, energy-efficient, and comfortable way to heat water for your home. If you are considering buying a new hot water cylinder, or if you need your existing indirect hot water cylinder serviced, be sure to contact a qualified plumber.

A hot water cylinder is a crucial component of your home’s hot water system. Understanding the different types and benefits of upgrading can help you make informed decisions that improve your quality of life while also reducing energy consumption and costs.

If you’re considering upgrading direct hot water, or need maintenance for your hot water cylinder, consult with a professional to ensure your system operates at its best. A well-maintained hot water cylinder ensures that you always have the comfort and convenience of hot water at your fingertips.

Remember, the key to a successful hot water cylinder system lies in choosing a water storage tank of the right type, and size, and maintaining it regularly.

Cylinder Repairs

Is your cylinder acting up? Leaking water pressure is low enough, making strange noises, or not providing hot water as it should? Don’t worry; MML Plumbing has your back. Our expert plumbers are skilled at diagnosing and repairing cylinder issues promptly.

Cylinder Maintenance

Regular maintenance is key to extending the lifespan and efficiency of your cylinder. MML Plumbing offers comprehensive maintenance services to keep your system in top shape.

Reliable Plumbers

MML Plumbing – Hot Water Cylinder Services

Hot Water Cylinder Installation

When it comes to installing a cylinder, you need a professional service you can trust. At MML Plumbing, we have the expertise and experience to handle cylinder installations of all types. Whether you’re upgrading to a more energy-efficient model or need a new cylinder for your home, we’ve got you covered.

Frequently Asked Questions

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