Across the UK, we all experience some chilly moments in the colder months, and we rely on our radiators to keep us warm. Most people know that their radiators run as a part of the central heating system, powered by hot water from their boiler.
Sometimes, things need to be done to our central heating systems – routine maintenance,repairs and servicing,new installations – and it becomes necessary to drain the system. This involves a process known as bleeding the radiators.
It may sound tricky and technical, but if you find that you need to drain your system, don’t be put off. It’s a fairly simple process and something that most people can do themselves with a few standard tools and a little bit of knowledge.
Combi boiler or conventional heating system, you’ll find the steps needed to drain your central heating here. So follow our guide, written by ourspecialist heating technicians, to learn how to drain your central heating system.
Why Drain the Central Heating System?
There are lots of reasons why you might need to drain the central heating, and the chances are it’s something that you’ll need to do sooner or later. First and foremost, taking good care of your heating system is important to getting and maintaining high performance levels.
It’s a good idea to undertake routine maintenance. This will involve draining and cleaning the central heating system to expel pollutants like rust, limescale and dirt. These are all things which can naturally find their way into your system and inhibit its performance.
If you’re planning some repairs to the central heating system or radiators, it will probably be necessary to drain them before you start work. And if you’re installing new radiators, you’ll want to get all the water out of the system before you disconnect the old units.
Heating professionals strongly recommend adding an inhibitor to the water in your system. This is a special mix of chemicals which prevents corrosion, and also extends a radiator’s lifespan and optimal heating performance. An inhibitor attacks those unwelcome pollutants and defends against them. You can add an inhibitor to the water before you refill the system.
Things You’ll Need
Draining the system and bleeding radiators is a relatively standard procedure, and as such you’ll be able to find most of what you need around your home or garden. Try to locate:
An adjustable spanner or wrench
A length of ordinary hosepipe or garden hose
The radiator bleed key
A jubilee clip (a special clip used to attach a hosepipe to a smaller pipe)
Some absorbent towels
A bucket and/or some large bowls
A flat head screwdriver
How to Drain the Central Heating System
Draining the system can be quick and painless if you follow the steps we’ve laid out for you here. Sometimes though, something a little more serious may be necessary. If you find that your boiler has given up the ghost, or you’re interested in a new boiler, get in touch today. Our friendly team can answer any questions and give you a free, no-strings quote.
Step 1: Turn off the central heating system
The first step in the process is to turn off the heating. This may sound simple but it’s an important safety measure, and you’d be surprised how many people forget to do it. You’ll need to wait for the hot water in the system to cool down, which usually takes 30 – 60 minutes. If your boiler runs from a solid fuel fire, put out the fire and wait for the hot water to cool.
Step 2: Turn off the water supply
This is an essential step – you definitely don’t want dirty water running through the system when you’re trying to drain it.
There are a couple of different ways you can cut the water. The first is to totally shut off the supply for the entire building. You can do this at the main stopcock – there’ll be a tap or valve, which you can turn on and off with a screwdriver. Be aware, though, that this will cut off the water to the whole property, and there will be no running water until you turn the mains supply back on again.
If your system runs on a conventional or regular boiler, you’ll need to isolate the heating tank. This means that there will be no new water going into the tank, and will allow the water currently in the system to drain. You should be able to find a tap or valve on the side of the tank. Then, switch off the boiler.
If you’re running a combi boiler, simply turn it off and wait for the system to cool. Not sure what boiler you have? Bbright can help you identify your boiler, and work out which model is the best fit for your home.
Step 3: Find the drain-off valve
(If none of your radiators have a drain-off valve, you have a slightly different system. Skip ahead to the next section).
Usually, a central heating system will have a main radiator. This is typically located on the ground floor, in a central position of the floorplan. The main radiator will have a small tap or drain valve attached to it – this is the drain-off valve (or draincock), and all the other radiators will drain through here.
Once you’ve located the drain-off valve, use a jubilee clip to attach the hosepipe to it. Check that it’s attached securely. To be on the safe side, put a few towels on the floor beneath it, as there’s no guarantee you won’t get a couple of drips.
You won’t want the drained water coming out anywhere in your home. Run the hosepipe through the house to a safe area outside. A street or gutter drain would be ideal. The drained water will probably contain some chemicals that you’ll want to keep away from plants and animals, so try not to drain the system straight onto the lawn or flowerbeds.
Step 4: Loosen the drain-off valve
Now it’s time to open the drain-off valve. Loosen it, and you should start to hear the water flowing through the hosepipe.
Next, go to all the other radiators in the house and open the drain valve, called the regulator (note: this is different from the temperature-controlling valve, and usually on the opposite side).
Step 5: Open the bleed valves
The next thing to do is release all of the trapped air from the system. To do this, open the bleed valve (using the radiator bleed key) on all radiators. You’ll hear a hissing or sucking noise when the air rushes out. A pro tip is to start with the upstairs radiators, wait 15 minutes, and gradually move to the downstairs radiators. This helps the system drain faster.
Don’t forget about any heated towel racks or spare room radiators on your way, and you’ll want to put some towels down, as opening the bleed valve can sometimes release one or two drops of water.
Check on the hosepipe. Once there is no (or very little) water coming through, the system is drained.
Step 6: Refill the system
Finally, you’ll need to put new water into the central heating system. If you’re adding an inhibitor, now is the time to do so. Close the drain-off valve and all the radiator bleed valves around the house.
Now you can safely turn the water supply back on. You’ll need to bleed the air from radiators again. This time, start with the downstairs radiators, and work your way up. Make sure that all the air is expelled from the radiators – again, you might see a couple of droplets coming from the bleed valve, so keep those towels underneath for now.
Tighten up the bleed valves, and check that each one is closed. Turn on the heating system and let it run. Check that all radiators are heating up, and that there are no cold spots – an indicator of trapped air. While you wait, have a look around the different rooms, and check all the radiator valves to make sure there are no leaks.
How to Drain the Central Heating System Without a Drain-Off Radiator Valve
If none of the radiators in your home have a drain-off valve, the process of draining your system will be slightly different.
Steps 1 and 2 are exactly the same procedure.
Next, you’ll need to isolate the radiator from the heating system. To do this, close both valves on the radiator – the regulator, which lets water in, and the lockshield, which controls the temperature. Then you can bleed the radiator.
Without a drain-off radiator valve, you’ll need another way to let the water out of the radiator. There will be a coupling nut, often located close to the regulator valve. Remember to put a bucket (or large bowls) and some towels underneath, and, using a spanner, twist the nut until the water comes out. Continue until all the water has drained.
Have a Question? We’re Here to Help
Hopefully, you should now feel ready to take on the draining of your own central heating system and be equipped with the knowledge to do so. But if you still have questions or concerns about draining central heating, or encounter a problem along the way, don’t hesitate to contact our professional team.
We’ve got years of experience dealing with all kinds of central heating systems, and we’re committed to providing our customers with the best value, best service and best customer experience. To ask a question about your system, or to discuss your boiler needs, reach out to us now.
