How to Drain a Radiator Safely: Step-By Step

drain radiator

Whether you’re looking to remove your radiator to redecorate, or if you suspect that there’s congestion in your radiator impacting your home’s heating, it’s handy to know how to drain a radiator.

But you might be wondering how to drain a radiator without draining your home’s entire heating system. In this step-by-step guide, we’ll explain how to safely isolate and drain a radiator, how to not make a mess while doing so, and when to call in the experts.

So, how do you drain a radiator safely? Let’s take a look.

Why drain a radiator?

There are many reasons you might want to drain a radiator:

  • You’re redecorating. If you’re getting some DIY done around the house and feel like repainting your home, you’ll need to detach the radiators to access each wall. It’s a good idea to drain the radiator before detaching it – this will make it lighter and easier to detach, while also preventing spillages on your carpet.
  • Your energy system isn’t working. If your home heating isn’t as efficient as it once used to be, there may be congestion in your radiators. Draining a radiator is the only way to deblock congestion and get your home thoroughly heated again.
  • Maintenance. To prevent congestion, it can be a good idea to regularly drain your home’s radiators. Regular draining can prevent gunk build-up, which can lead to your radiator being inefficient.
  • Leaking. If you notice a leaky radiator, you should disconnect it right away and drain it. Leaving a leaky radiator full can lead to water damage in your home.  

How to drain a radiator: UK heaters edition

In order to drain your heater without totally cutting off the energy system, follow our step-by-step guide below:

Step 1: Gather your toolkit

Before you can drain your radiator, you’ll need to gather a couple of essential tools. Here’s what you’ll need:

  • An adjustable wrench
  • A spanner
  • Thick black plastic bags (or another form of protective covering for your carpet)
  • Your radiator key
  • A basin, a shallow bucket or a hosepipe

Once you’ve gathered everything you need, you can begin draining your radiator. 

Step 2: Turn off the thermostat

Before you can begin draining the water from the radiator, you’ll need to make sure that the thermostat is turned off. Using the thermostat at the side of the radiator, turn it clockwise until it is set at 0. If you’ve been using your radiator just beforehand, you’ll want to wait between 30 minutes to an hour, to ensure that the water has completely cooled. (Draining hot water increases your risk of burns.)

Step 3: How to drain a radiator without draining the system?

If you’re only going to be draining one radiator, you probably don’t want to cut off the whole heating supply in your house. To prevent this, you’ll need to isolate your radiator. 

Once you’ve turned off the thermostat, you need to shut off the water valve to your radiator. You can do so using a spanner or your adjustable wrench. This will prevent any new water from entering into the radiator from your water system, and won’t shut off your home’s heating entirely. 

Step 4: Protect your carpet and ceilings

Draining a radiator can be a messy business, especially if you’re dealing with any type of leak. In order to protect your home’s carpet, you’ll want to lay down a protective cover around the radiator.

For this, you can use high-density black rubble bags. These are often better than protective covers, as they’ll collect any leaking water and make it easy to transport any water that spills out of the radiator. Flat protective covers can work, but they can still cause water damage when lifted up or moved.  

If you’re draining a radiator in a flat or on the second or third floor of your house, you’ll want to be extra careful about leaks. Leaking radiator water can seep through the carpet and end up damaging the integrity of your ceiling or floor. You can place the rubble sack around the radiator valve for extra protection. 

Step 5: Begin draining the radiator

Once you’ve protected your carpet, grab your basin or shallow bucket. Place it directly under the valve to ensure no spillages. Slowly, unscrew the valve and let the water begin to flow into the basin.

If you prefer, you can also attach a hose pipe to your radiator and drain it in your sink. Using a hosepipe can be a more efficient way to drain a radiator, but might not be convenient if you’re draining a radiator room far away from the bathroom or kitchen. 

For rooms that don’t have the benefit of a nearby sink or shower, you can use a shallow basin to get the job done. Make sure that your basin or bucket is large enough to contain all the water being drained; it’s a good idea to have a spare on-hand in case it overflows.

If your basin is nearing the brim but your radiator is still draining, you can simply re-close the valve, empty the water into the sink or shower, and restart the process. 

Step 6: Speed up the process

It might take around 15-30 minutes for one radiator to drain completely. Unfortunately, you shouldn’t go off for a tea and a biscuit while you wait for it to drain. We’d recommend monitoring the drainage closely to ensure that there are no spillages, and to ensure that the basin doesn’t overflow with water. 

You can speed up the process if it’s taking too long. If your radiator is draining slowly, you can adjust the valve so that more water comes out. You can also make use of the radiator key to speed things up: insert the radiator key into the keyhole and allow some air into the radiator. This can help the draining process complete faster. 

Step 7: Repeat on the other side

Once you’ve finished draining one side of the radiator, you can repeat the process on the other side. If you suspect a leak, we wouldn’t recommend draining both sides of your radiator at the same time. While it can be tiresome and time-consuming to drain one side at a time, it’s safer when it comes to managing any leaks or spillages. 

When to call the experts

Our step-by-step guide above is a safe way to drain your radiator if you suspect there’s a problem. But what problems constitute a phone call to drainage services?

If you suspect that there’s a leak coming from your radiator, it’s best to call in the experts. Find a drain unblocking service UK rather than handling it yourself; experts will be able to establish the root of the problem and fix it correctly. 


Can you drain individual radiators?

Yes. You can isolate a radiator by turning off the valve that leads to your home’s water supply.

Do you bleed a radiator when it is on or off?

Never drain a radiator that is on. Switch the thermostat to zero and wait thirty minutes before draining a radiator that has been recently turned on.

How long does it take to drain a radiator? 

Depending on the size of the radiator, it can take anywhere between 15 minutes to an hour to drain a radiator. If your radiator drains incredibly fast, it might be a sign of gunk and congestion accumulating in the bottom of the radiator.

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