How to Drain a Central Heating System

Up2Speed Marketing Ltd • July 2, 2025

To keep your central heating system in good working order, you’ll need to maintain it properly. Unless you look after your central heating system, the system is unlikely to function as it should. Occasionally your central heating system will need to be cleaned and drained. Perhaps you’re not sure how to drain a central heating system? If you’re looking to learn, this central heating guide can help.


First of all, it’s important to understand that there are several different types of central heating system.

Types of central heating systems

1 . Conventional Central Heating Systems

Many homes are fitted with a conventional central heating system; these systems tend to rely on gravity. A conventional system is built with a water tank that’s positioned at height (for example in a high cupboard, a top floor, or in the attic). The system works because gravity moves the water downward, using a natural process, as opposed to artificial pressure.


Generally, you’ll find conventional central heating systems in older homes. The issue with these systems is that they are built with pressure limits, and it’s difficult to increase these pressure limits. Conventional central heating systems tend to waste energy, so it’s rare that you’ll find these in a newer home.

2 . Pressurised systems

Pressurised heating systems use a water cylinder to heat the mains water. The cylinder is like a small tank, and you can place it pretty much anywhere inside your property. Pressurised heating systems do tend to be expensive, and you’ll need to perform regular checks on these central heating systems. One of the best things about a pressurised heating system is that they are incredibly efficient.


If you have a pressurised heating system, you’ll need high mains pressure to keep the system functioning. When you have a pressurised system, you can use multiple appliances without experiencing pressure drops.

3. Combi Boiler Systems

Combi boilers are considered the most efficient type of boiler. These new central heating systems retain pressure and are helpful to save energy. When you use a combi boiler system, you won’t need to use a water tank, which helps save space in a smaller home. Combi boiler systems are the most common type of boiler system for a modern home.

4. Electric central heating system

As the name suggests, electric central heating systems are boilers that are powered by electricity. These systems do not use a traditional boiler; all you have to do is plug them in. There are several benefits of using an electric system:


  • Less expensive running costs.


  • Simple installation.


  • Improved energy efficiency of your home.

Central heating system diagram

Sometimes referred to as a ‘combi boiler’. A few of the key benefits of having a combination boiler system include:


  • These are compact (meaning they are ideal for small houses or flats).


  • You don’t have to worry about the pipework freezing in the loft.


  • The central heating system pressure remains consistently high.


Gravity-fed heating systems are also known as conventional heating systems. As previously mentioned, these are usually found in older homes and tend to be less energy efficient. The flow relies on gravity, and so the water pressure isn’t always great. This type of house heating system needs an expansion tank and a tank for cold water storage. Both tanks are usually installed in the loft.


A pressurised boiler system is a high-performing system; however, you can expect to pay more compared to a combi boiler system. Unlike a combi system, these boilers do rely on a hot water tank.

How to drain a central heating system

Step 1: Turn Off The System

The first step is to make sure that your central heating system is switched off. Before you begin draining the system, you should ensure that the pipes and the radiators have completely cooled down.

Step 2: Extinguish the fire

Does your boiler have a solid fuel fire? If so you’ll need to put this out, and then wait until your boiler has turned cold.

Step 3: Turn off the water supply

Next, you should turn off the water supply that’s connected to your boiler. Doing so will stop the water from entering the unit while you’re working on the system. Look for a stop tap; if you can’t locate one, find the ball valve and tie it up to the wooden latch (this should be located on the cistern, at the top).

Step 4: Locate the drain-off valve

Now you’ll need to locate the drain-off valve; this should be on one of your radiators, usually a radiator on the first floor of your property. The drain valve should be at the bottom of one of your radiators. Take a garden hose and attach it to the outlet. You can use the hose to run the water outside. Use a clip to keep the hose pipe secure and ensure that it doesn’t fall off.

Step 5: Bleed the radiators

Next, open up the bleed valve; this will allow the water to run through the system. Begin by working on the radiators nearer the top of your property; this will mean that the water runs faster. After approximately 15 minutes, you can also open the valves on your downstairs radiators.


If there’s any air trapped in the system, this may stop the water running. If this happens, you can fill your tank.

Step 6: Open up the drain valve

When you’re draining a central heating system, you’ll need to open up the drain valve and let out the water. All of the radiator valves should be open. Go to the valve that’s attached to the hosepipe and use this to drain down the central heating. The procedure should take approximately 30 minutes to one hour. If you open all the radiator bleed valves, this should make the process quicker.

Step 7: Refill the system

Once the process is complete, you’ll need to fill up the central heating system once more. First, close the valves that you opened before, and close the radiator drain cock. When you’ve filled up the tank, you should bleed the radiators downstairs also. Adding an inhibitor can help you to prevent limescale build-ups and limit corrosion. Next, tighten up all the valves and then turn on your power supply. Once the system heats up, you should bleed the radiators once again. Check the valves and joints, and make sure there aren’t any leaks.

Why do I need to drain my heating system?

Draining down your central heating system will help you to maintain the efficiency of your boiler and avoid any issues. You might need to drain your central heating system if you’re changing your radiators, fixing a leak, or removing limescale and sludge.

How do you drain a central heating system without a drain valve?

Perhaps your radiators do not have a drain-off valve? If this is the case, you’ll need to take a slightly different approach. First, you’ll need to make sure that you have the following items:


  • A speed fit tap.
  • An adjustable spanner.
  • A pair of pliers.
  • A hosepipe.
  • Towels.
  • A large bucket.

Step 1: Switch of the system and the water supply

The first thing to do is to turn off the central heating system and then let the radiators cool down. If your property has a conventional boiler, you’ll need to isolate the water before you turn the boiler off.

Step 2: Separate the system and the radiator

The next step is to separate the central heating system and the radiator. To do this, you can close the valves that are located on the ends of the radiators. At one end of the radiator, you’ll see a thermostatic radiator valve; once you’ve located the valve, you can turn it clockwise. At the opposite end, there should be a lockshield. When you find this, take off the plastic cap and use the pliers to close this valve.

Step 3: Bleed the radiators

Bleeding the radiators will help you to drain your system faster (make sure that you let out all the air).

Step 4: Loosen the nuts

At this stage, you’ll need to loosen up the union nuts. Go to the TRV end of the radiator, find the coupling nut and release it. Position the old towels and the bucket underneath; this will help you to catch spilled water. Next, take the adjustable spanner and turn the nut in an anti-clockwise direction. Now the water will start flowing out.

Step 5: Drain the system

Ensure that the radiator valve is switched to ‘off’, attach the hose, and use this to drain the system. (To attach the radiator and the hose you’ll need a speed-fit tap).

Contact Aquatek Today

If you’d like to learn more about draining your central heating, contact Aquatek today.


 Aquatek Plumbing offers a wide range of services including boiler service and repair, bathroom fittings, power flush, central heating, and more. Whether you’ve got a gas central heating system, an oil central heating system, or an electric system, Aquatek can offer the best maintenance support.

Why is My Boiler Losing Pressure

By Up2Speed Marketing Ltd • July 2, 2025
One of the main calls that most plumbers receive every year, is the question ‘why is my boiler losing pressure?’. There could be many reasons as to why the boiler may be losing pressure, but the main factor in why it could be is that there could be a leak in the system somewhere. Some of the parts that could be leaking, could be the radiator valve, a pipe or something else that could be allowing the water to escape the system, then causing the loss of pressure within the boiler. However, they are not the only things that could cause a boiler to lose their pressure. There could be a problem with the valve on the boiler that could have possibly started to fail, in turn causing a drop in the pressure inside the boiler.

Common Central Heating Problems & How to Fix?

By Up2Speed Marketing Ltd • July 2, 2025
We all rely on our central heating systems, and that makes it even more frustrating when a problem arises with yours. These problems often arise when you turn them on after long periods of disuse. To avoid problems, you should turn the heating on periodically throughout the summer so those periods of disuse aren’t as long. We’re going to talk about what can be done to fix any problems you might experience with your heating system, as well as some of the most common problems that might cause those problems to begin with. So read on now to find out more.

How Much does a Boiler Service Cost?

By Up2Speed Marketing Ltd • July 2, 2025
Boilers are built to last, with a life expectancy of up to fifteen years but as with anything, problems can and do occur. This is especially true overtime when it comes to older models. Parts can wear out, and eventually, need repairing or replacing completely causing you a number of problems along the way.

What Boiler Size do I Need?

By Up2Speed Marketing Ltd • July 2, 2025
Picking the right boiler for your home is very important. Whether you’re replacing one that’s broken or need to get a new one that works better for your property, it’s a task that needs plenty of research. Boilers aren’t cheap after all, and you want a central heating system that’s going to provide everything you and your household needs on a daily basis. But what boiler size do you need? Most of us will have little knowledge of the variety of boilers out there, let alone what each one can do to benefit the home. So with that being said, here are some tips on picking out a boiler size that’s perfect for your property.

Why is My Central Heating Noisy?

By Up2Speed Marketing Ltd • July 2, 2025
Central heating is something that shouldn’t be loud and obtrusive when it comes to the noise it makes. If your central heating has been well maintained, then you shouldn’t really experience anything too loud when it’s being used. However, there can be cases where your central heating is louder than usual or makes regular noises that might include banging, gurgling, or even dripping sounds. With that being said, here’s why your central heating might be noisy.

Bathroom Fittings Buying Guide

By Up2Speed Marketing Ltd • July 2, 2025
‘Bathroom fixtures, toilet fittings, bath and shower fixtures’ – you can see how these words can quickly become confusing bathroom terminologies when you are renovating your bathroom. Out of the many different terms, ‘bathroom fittings’ sounds simple enough, but what exactly does it mean? This guide seeks to help you understand precisely what bathroom fittings are and give you an understanding of some of the bathroom fittings lingo you may hear during your project.

How To Bleed a Radiator Without a Key

By Up2Speed Marketing Ltd • July 2, 2025
Winter is well and truly on our doorsteps, and we all need our heating systems and hot water to be running smoothly. So if you find that your radiators aren’t heating up correctly, the room feels cold even with the heating turned up, or the radiators you have are cold to the touch at the top, then the first thing to try is bleeding your radiators. When air becomes trapped inside the radiator, it can affect the performance of the unit and result in a partially heated or cold room. This occurs from time to time, but as it’s not every day, frequently people misplace or lose their radiator key. Before you give up, there are a few substitutes that you can use to get the job done.

No Water or Low Water Pressure?

By Up2Speed Marketing Ltd • July 2, 2025
Having low water pressure is an extremely annoying problem. Even worse is turning on a tap in your home to find out that you have no water. When this happens, you need to act fast to restore running water in your home. Low water pressure can do more damage than merely inconveniencing you. For instance, it can damage appliances like the dishwasher and the water heater. This is because these appliances require specific water pressure to work effectively. If they are continuously operating with low water pressure, they may get damaged, and you may even have to replace them. So, what causes low water pressure? And what can you do if you encounter this problem? Read on to find possible causes and practical solutions to your low water pressure problem.

How to Plumb in a Washing Machine or Dishwasher

By Up2Speed Marketing Ltd • July 2, 2025
A washing machine or dishwasher is not only convenient for the house, but they are also easy to use. These machines come in handy when it’s time to clean up the house and do laundry. Here is why: They eliminate physical effort where you don’t have to use your hands to wash clothes and clean dishes. It saves time since the machines perform all work, which includes cleaning and drying. So, you can multitask and finish on time. They perform quality work compared to using your hands, which can miss out on stains. They protect clothes from getting damaged while avoiding careless dropping of dishes. Washing machines and dishwashers continue to make life easy. That is, they provide new technological advancements with each new make. Such include different sizes to fit in different house spaces, while others provide a variety of setting options to choose from, where the type of cleaning depends on material and color of clothes or type of dishes. But without careful plumbing of the dishwasher or washing machine, it can be difficult to use them. The average time a person can take to install these machines is two hours. If you don’t know how to do it, consider hiring a plumbing specialist. Luckily, you can learn how to install a washing machine or dishwasher with this simple guide. These tips can help you avoid an additional fee for installation. Let’s dive in.

How to fix a toilet flush button – Replace toilet flush button

By Up2Speed Marketing Ltd • July 2, 2025
You never consider how to fix a toilet flush button until you break yours and you don’t have a choice. When you face a flushing problem in your toilet, it can cause some trouble and make your toilet impossible to use. This is always going to be an issue – you need to use your toilet, and you need to be able to flush it, too. Today, we’re going to talk you through how to fix a toilet flush button!
Show More