You'll likely notice some drips emerging when initially turning the
It's perfectly normal for some amount of water to come out when you bleed a radiator. If a large volume of water has poured out, it's possible that you opened the valve fully. We recommend not opening it all the way.
The point of bleeding a radiator is to let air out. The radiator should be full of hot water. If it's full of air, it's not heating.
If you let too much water out of a radiator, the overall pressure in your central heating system can drop. This may result in the boiler shutting down or the heating system malfunctioning.
You should drain your central heating system to maintain it from time to time. By not draining it, you risk the system having issues, and issues cost money. It should be drained when installing a new radiator, removing an old one, or putting an inhibitor into the system.
Simply draining the radiator may get rid of most of the old antifreeze but could leave some coolant and contaminants behind, which would then mix with and pollute your new antifreeze and cause overheating. You want a full flush, a forced removal of anything old so you can pave the way for new fluid.
We want to make sure that no water comes out. Occasionally you'll get a bit of water come out as the pressure dissipates from the radiator, but it should stop quickly.
Aside from the danger of working with a radiator that has the heating on, it's also an inefficient bleeding process. If the pump is running when you let out air, this will actually cause the system to draw in more air from elsewhere.
Coolant systems don't normally have a lot of extra room at the top, so the fluid levels should be near the top. If the fluid is more than a few inches from the cap, it's probably low. Look for the “full” or “fill” line etched into the radiator metal. That is where the coolant should be.
What do you do when bleeding radiators but no air or water is coming out? If no water or air comes out when you bleed the radiator, then the valve could be blocked with paint. Close the inlet and outlet valve at each end of the radiator, then remove the screw from the centre of the bleed valve.
If a radiator is cold at the top, then it needs bleeding. If it's not, then just leave it be – you don't want to bleed a radiator that doesn't need bleeding. If you decide you need to bleed the radiators, remember to turn the heating off before moving on to the next step.
It's advisable to check first whether it's a stuck pin, as these sometimes get stuck in an 'off' position, which needs a quick wiggle to release the pin and allow the water to flow. However, valves can break down, and older radiators may well have degraded thermostatic valves, especially if they're used often.
On the side of the reservoir, it has an L(low) and F(full) markings, and as the tank is translucent, you can see your coolant level without opening the cap. If the fluid is close to or below the L marking then you need to add more coolant to the reservoir.
Usually, it will take between 20 and 30 seconds to effectively bleed a radiator, but it might take up to a full minute in the case of larger radiators.
Air pockets, inadequate water pressure and faulty radiator valves or TRVs are the three primary reasons why radiators do not work after bleeding.
Everything you may want to know about bleeding your radiators is covered in this guide, including the labour costs and time frames you should expect. To give you a quick idea, the average cost to bleed a radiator is usually about £100.
Yes, it is perfectly normal for water to escape when a radiator is bled. You'll likely notice some drips emerging when initially turning the bleed screw in an anti-clockwise direction. And water would pour out once the air was released, if the valve was to be opened fully.
If you're filling the radiator, add coolant until it's completely full, just below the rim of the filler neck. On the reservoir, identify the markings for FULL and LOW that are stamped in the plastic. There may also be indications for HOT and COLD. With a cold engine, add coolant to the FULL or COLD mark.
If your radiator is low while the coolant reservoir remains full, a possible explanation is a coolant leak in the cooling system. Inspect the hoses, connections, and radiator for any visible signs of leaks. Additionally, check beneath your vehicle for puddles of coolant, which could indicate a leak.
Open the bleed valve to release air
You should hear a hissing sound as the trapped air begins to escape. Be prepared for water to come out as well, so keep your container or old towel close to hand. Slowly keep turning the valve anticlockwise until the hissing stops and water flows steadily.
Why is the water black when I bleed my radiator? Black or discoloured water is usually a sign of internal rust or sediment buildup within the system. Over time, corrosion can occur, leading to the accumulation of debris in the system. Flushing the system and addressing the source of the corrosion is recommended.
Bleed a radiator
We've written an article on bleeding radiators here, but in summary, locate the bleed valve on a radiator, place a bucket or tub underneath or next to the valve, and open the valve gently. Water will squirt out, so you should also protect any wallpaper and carpets nearby.
The amount of water in a radiator is typically determined by the size of the radiator and the capacity of the heating system. Radiators are often designed to work in conjunction with a specific heating system, so the amount of water they hold will be optimised to work efficiently with that particular system.
Just a half turn will do in most cases. No more than a full turn is ever needed. Have a towel handy to catch the dribble of water, often it's dark and dirty and may stain walls and carpets. Do not taste this water, it can contain chemicals and/or bacteria.