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As a homeowner, maintaining your central heating system regularly is essential for it to last. To keep it working right, you should drain and clean it occasionally. Why would you want to drain your central heating system? Do you know how to do it? If you still need to, we’ve prepared this step-by-step guide to help you out.

Why Is Draining a Central Heating System Necessary?

Sometimes, maintenance is one of the many reasons for draining your central heating. This will also be necessary when you’re up to removing a radiator or fitting a new one, or when you’re about to add an inhibitor to your system. It’s also helpful to drain the central heating to eliminate sludge and limescale. And let’s not forget that some heating or boiler repair works can’t be dealt with without draining the whole system down.

Before divining into our easy tip-follow, in-depth guide on How to Drain your Central Heating System, it’s essential to know that DIY fixes are sometimes unsafe.

What Tools are Required?

  • Radiator key  
  • Jubilee Clip  
  • Hosepipe  
  • Towels 
  • Bucket  
  • Adjustable spanner

Do not attempt DIY if

  • It would help if you were more confident in your ability to follow a step-by-step guide.
  • The system shows signs of significant damage.
  • It would help if you had proper safety equipment and tools.

Talk to a heating tech if any of these things happen.

Draining your central heating system for the first time can seem daunting, but it can be a straightforward process with the proper knowledge and preparation. 

Here Are Some Essential Tips To Ensure You Do It Correctly

Essential Tips To Drain Your Central Heating 

Turn off the system Before you begin, make sure to switch off your central heating system completely. This will prevent any accidents or damage while you work on draining it.
Switch off the water supply The next step is to turn off the water supply to the boiler. This keeps water from getting into the system or boiler while it’s being drained. Stopcocks or separation valves are common parts of boilers.
Locate the drain valve Find the drain valve on your central heating system. It’s usually located near the bottom of the boiler or radiator. Use a wrench to open it slowly and allow the water to flow out.
Prepare for leaks Place a bucket or tray under the drain valve to catch any water that comes out. Also, lay down towels or newspapers to soak up any spills.
Ventilate the system Open any bleed valves on your radiators to allow air into the system, which will help the water drain more efficiently.
Monitor the process Monitor the water level in the system as you drain it. Once fully drained, close the drain valve tightly to prevent leaks.
Refill and bleed Once you’ve finished draining the system, refill it with fresh water and bleed the radiators to remove any air bubbles.


Following these tips can make draining your central heating for the first time a stress-free experience, ensuring it runs smoothly and efficiently in the future.

How do I drain my central heating system without a draining valve? 

  1. Repeat steps 1 & 2. 
  2. Separate the radiator from the heating system and close its two valves; Regulator and Lockshield. 
  3. To close the regulator, rotate it clockwise. 
  4. To close the lockshield, remove the plastic cap and tighten it with a plier. 
  5. Bleed your radiators by opening the bleed valves to let the air out. 
  6. Now locate the coupling nut on the regulator/TRV. 
  7. Put a bucket and cloth beneath this coupling nut and spin it anticlockwise with an adjustable tool until water streams out.
  8. Keep an eye on this and tighten the coupling nut when the bucket is full. Fill the water up, then carry on. Alternatively, use a speed-fit tap to attach a pipe to the radiator drain.

how to drain a central heating

Do I Need a New Boiler?

Determining if your central heating system needs a new boiler. Key indicators show a replacement unit may be needed.

  • Firstly, age factors heavily. Boilers normally have a lifespan of ten to fifteen years. Your boiler’s efficiency may drastically decrease if it is nearing or beyond this age range.
  • One must also consider frequent breakdowns. Occasional issues may not warrant a complete replacement, but if breakdowns become regular, the cumulative cost of repairs and potential heating inefficiencies make a new boiler a more cost-effective solution.
  • Energy bills can also give you a clue. Increased energy bills may indicate that the boiler consumes more energy to provide the same heat, raising prices. This generally indicates system inefficiency.
  • Furthermore, odd noises like gurgles, whistles, or fringe could mean that an internal component—like the heat exchanger—is broken. Such problems suggest that the boiler needs help to operate effectively.
  • Boiler costs vary depending on several factors, including their brand, model, fuel, output, warranty, labor, and installation type. 

A new boiler will often set you back between £1,845 and £3,500, but if you don’t have a budget, then you don’t need to worry about it; the UK government has initiated ECO4 free boiler grant scheme for eligible homeowners living in the UK if you want to enroll yourself, firstly you may need to check your eligibility with [company name+internal link], after meeting with eligibility you need to fill our application form to proceed your status. 

 How long does it take to drain a central heating system?

It can take 20 minutes to over an hour to drain your central heating system completely. This depends on your system, whether or not you have a drain-off valve, and whether or not you run into any issues during the process.

To speed up the process, don’t forget to open the bleed valves on each radiator. This will improve the water’s suction and encourage its drainage.

When draining a central heating system, remember that your boiler will not work during that period. If you have closed off the water supply at the mains, you will not have access to any water during this time. To ensure there are no issues, keep this in mind before beginning the process.


Draining your central heating system for the first time might seem daunting, but following these simple tips ensures a smooth and efficient process. Remember to turn off the system, locate the drain valve, prepare for leaks, ventilate the system, monitor the process, and refill and bleed the system afterward. These steps will help prevent accidents, ensure proper maintenance, and keep your central heating system running smoothly. With a bit of preparation and care, you can successfully drain your central heating for the first time, maintaining its effectiveness and longevity for years to come.


The timeframe can vary depending on the workload of your chosen installer and the availability of boilers. However, once your application is approved, you can expect the installation in a few days.

Anyone who has a boiler installed before 2005 or has an inefficient boiler can qualify for a boiler grant in the UK. To meet the requirements, you must be a homeowner or private tenant of the home in the UK.

The ECO4 Scheme is a government-funded program that provides grants and funding to homeowners in Scotland, who want to install energy-saving measures in their homes. The aim of the Eco4 scheme is to help people reduce their energy consumption and save money on their energy bills.

Yes, it’s quite easy. You should regularly check that the evaporator and air intake grill are clear of leaves and other particles.

To be eligible for a first time central heating grant, you must not have prior central heating installed in your homes. Also your home’s EPC rating should be lower than D.