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Draining Your Central Heating via a Radiator: A Step-by-Step Guide

Draining Your Central Heating via a Radiator: A Step-by-Step Guide




If you’re facing the need to drain your central heating system but can’t find a drain cock, don’t worry—you can still do it through a radiator. While this method takes longer and can be more labor-intensive, it’s essential to know how to do it, especially in emergencies. Below is a step-by-step guide to help you effectively drain your central heating system through a radiator, ensuring a smooth process and offering tips for future maintenance.


Step 1: Locate and Remove the Radiator

First, you’ll need to remove a radiator from the wall. It’s best to choose a radiator located on the ground floor or in the basement. Ideally, select one in a wet room, such as a bathroom, to manage any potential water spills more effectively. Removing the radiator gives you access to the radiator valve, where you’ll be connecting the drainage setup.


Step 2: Prepare the Hose Connection

To drain the system, you’ll need to connect a hose to the radiator valve. Here’s how you can do it:

  1. Insert a piece of copper tubing into the end of a hosepipe.

  2. Secure the tubing in place using a jubilee clip to ensure it stays firmly attached.

  3. Push a flexible tap connector onto the copper tube.

Radiator valves typically come in two sizes: 1/2 inch for most modern systems and 3/4 inch for older systems. Make sure you have the correct connector size—either a 15mm to 1/2 inch flexi tap connector or a 15mm to 3/4 inch flexi tap connector. Mixing metric (millimeters) and imperial (inches) measurements may seem odd, but it’s necessary when purchasing fittings from a plumbing shop.



Close-up of a copper tube being inserted into the end of a hosepipe and secured with a jubilee clip to ensure a firm attachment. The image illustrates the process of preparing a hose for connection to a radiator valve during central heating system maintenance.
Securing Copper Tubing in Hosepipe with Jubilee Clip


Step 3: Attach the Hose and Open the Radiator Valve

With the hose and connector ready, attach the tap connector to the radiator valve. Tighten it by hand, and then give it an additional three-quarter turn with an adjustable spanner for a secure fit. Run the hose to an outside drain or a suitable drainage point, and then open the radiator valve by turning the head anticlockwise. You should hear water beginning to flow out. At this point, check for any leaks at the radiator connection and ensure everything is functioning properly outside.



Close-up of a person attaching a hose to a radiator valve, securing it with a tap connector and adjustable spanner. The hose is directed towards an outside drain, and the radiator valve is being opened to start the water flow. The image highlights the importance of checking for leaks and ensuring proper drainage.
Attaching Hose to Radiator Valve and Draining System

Step 4: Manual Draining Option (If No Hosepipe Available)

If you don’t have a hosepipe or can’t connect one to your radiator valve, you’ll need to drain the system manually. Place a large container under the radiator valve, open the valve to fill the container, close the valve, empty the container, and repeat this process until the system is completely drained. Be prepared—this method is time-consuming and can get messy, so having a drain cock installed in the future can save you a lot of hassle.


Step 5: Cleaning the System While Draining

If your main objective is to clean your central heating system, it’s a good idea to start the filling loop while the draining setup is in place. This will help flush out debris. Additionally, you should add a cleaning agent to the system. Choose a radiator on the upper floor for this process, as this will ensure the entire system gets thoroughly cleaned. The cleaning agent will help dislodge corrosion and clear any blockages. Follow the product’s instructions carefully, leaving the agent in the system for the recommended time before draining it out completely.


Step 6: Refilling Your Central Heating System

Once you’re ready to refill the system, double-check that all washers are intact and that the drain cock (if used) is securely closed. If you removed a radiator, make sure it’s properly reinstalled. For high-pressure systems, use a filling loop—usually a valve located below the boiler—to refill the system with water. While doing this, keep one of the radiator vents open at the top of the system to allow trapped air to escape. Once water starts coming out, close the vent.


Step 7: Bleed the Radiators

After refilling, you’ll need to bleed the radiators to remove any remaining air from the system. Start with the radiators on the lower floors and work your way up. This ensures that all air pockets are eliminated, which helps maintain an even heat distribution throughout your home.


Step 8: Final Checks and Adding Corrosion Inhibitor

Finally, check the boiler pressure. It should be between 1-2 bar, with 1.5 bar being ideal. Too low, and air can enter the system; too high, and you risk damaging components. Before you finish, don’t forget to add a corrosion inhibitor to the system. This chemical helps prevent internal rusting and prolongs the life of your central heating system. Follow the manufacturer's guidelines on how often to replace the inhibitor to ensure ongoing protection.

If you have a gravity-fed system, you’ll need to isolate the feed and expansion tank from the mains cold water supply before you start draining. When refilling, simply reverse the isolation process to restore normal operation.


Conclusion: The Importance of Drain Cocks

Draining your central heating system via a radiator is possible, but it’s a time-consuming process. Installing a drain cock can save you a lot of effort in the future. Whether you’re performing routine maintenance or addressing an emergency, understanding this process will help you manage your central heating system more effectively. Don’t be discouraged—it may seem complex, but with the right tools and a bit of patience, you can do it!


Discover more about sustainable building practices, detailed plumbing techniques, and design strategies on our Plumbing Design Blog. From securing copper tubing in hosepipes to attaching connectors for draining your central heating system, we cover everything you need to maintain and improve your home’s plumbing.

For further inquiries or assistance, feel free to contact us.


Disclaimer:

The information provided in these posts is for informational purposes only and should not be considered design advice, specifications, or a calculation template. We assume no responsibility or liability for the use of the information presented. For professional advice or design services, please contact us via our contact form.






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