What does it mean to bleed a radiator, and why would you want to do it? It sounds a bit boring and potentially risky, but it could turn out to be important maintenance.
Have you noticed cold spots at the top of your radiator? Or are you not feeling the heat when you switch one (or more) on? We’ve got the solution to those problems—and it might be a lot simpler than you think.
How to Bleed a Radiator
To bleed a radiator, you’ll need a few simple tools and a bit of time. Thankfully, it’s not an involved process, and you won’t need an expert to do it. Oh, and by the way! It should be called venting!!
Get the right tools
Depending on the type of radiator you have, you might need either a radiator key, a flathead screwdriver, or a pair of pliers. Check out the bleed valve on your radiator to see what tool you’ll require. You may also want a pair of gloves to protect yourself, plus a towel or even a bowl to collect any water that escapes.
This typical older type valve will need a radiator key, if its slighty worn you can GENTLY try needle nose pliers
This newer type of valve will take both flat head screwdriver or radiator key
If your key seems loose jump to the ‘My vent valve is ‘rounded off’ or too small, what do I do?’ section further down.
If you don’t have a rad key, and you have older radiators we would advise one without the chamfered inner edge or get a selecetoion like these https://www.amazon.co.uk/ShieldUp-Radiator-Valve-Bleed-Different/dp/B07BK7T3Y5/ref=sr_1_13?keywords=radiator+key&qid=1558520929&s=diy&sr=1-13
Locate the Bleed Valve
The bleed valve will always be on the top of the radiator, and most likely on either side. Sometimes, it’s a bit more difficult to find at the back of the radiator about 60mm in from the end. If its not on the side use your fingers to feel round the back, feel for a small square in a circular hole as the pic below, these types of radiators require a radiator key.
Open the Bleed Valve
Now it’s time for your radiator key or other tool. Use the tool to turn the valve about half a turn (counterclockwise). You might hear a hissing noise; that means air is beginning to escape. Be aware it may also drip.
Allow Air to Escape
Give the air time to escape—wait until the radiator starts ejecting water with no air (keep that bowl or towel handy) then shut the valve. When the water runs clear with no air, all the air has left the radiator.
Close it Back Up
Tighten the valve back up, don’t worry about doing it up tight, just as long as the drips stop. Infact its very common to round off the valve when doing it up too tight, causing issues when you want to do it again.
Repressurise system
If you have a pressurized system you may need to top up your system pressure to approx. 1.5 Bar, your boiler will usually tell you if the water pressure is too low. This is usually done at the boiler on a flexible. If you have a tank fed system this isn’t required.
Dry up any water remaining, and that’s it!
Automatic radiator air vents
Its worth noting that there are automatic radiator vents out there. The most well known being the Aladdin there’s mixed views on whether these should be fitted. The pros are clear but the cons consist of reasons such as giving the ability to allow air to be dragged in, masking issues with air or corrosion and leaking.
My vent valve is ‘rounded off’ or too small, what do I do?
Theres a few tricks of the trade you can try if your rad key is loose fitting or the valve has rounded off meaning you can’t get any purchase...
Before trying these you need to Make sure the rad can be isolated for the worse case scenario. To do this just close both valves either side of the radiator by rotating them clockwise.
You could first try using a spanner on the nut holding the valve in place (if it has one), or the nut at the opposite end at the top. It may need a square radiator tool like this https://www.amazon.co.uk/Plumb-Pak-T615AMZ-Radiator-Allen/dp/B002OB4COS
crack it open allow to hiss until the air is out and reclose.
This isn’t however always possible and can be a little risky but there are other ways to remove the bleed valve. We have listed these below, but be aware if you do get it out be sure to have a new replacement near by or you may end up in the same predicament next time you bleed them.
- Try a needle nose plier, be gentle though, you could make things much worse!
- Cut your bleed key down. As mentioned previously, quite often bleed/vent keys have a chamfered inner edge. By cutting or filing this off you can obtain a tighter fit at the back of the valve and perhaps gain enough purchase to vent the radiator.
- Use screwgrab, this stuff adds a bit of friction if you feel its close but slipping. https://www.amazon.co.uk/Todays-Tools-Screwgrab/dp/B0000DD2JZ
- Try these clock keys, Typically, radiator keys and vent valves are 5mm across, older ones may have either worn down or may just be slightly smaller from imperial measurements. Clock keys are also square, they come in a variety of sizes, the size 9, 10, and 11 keys are respectively 4.5mm, 4.75mm and 5mm in size. This should almost certainly get you out of trouble provided the valve hasn’t rounded off too much.
- If you have them lying around, use a 4mm, 4.5mm, 5mm or 5.5mm socket knocked on lightly with a hammer and turn with a ratchet.
- You could these screw extractor pieces, they could grip on to the valve and are treaded in a way that tightens whilst you rotate anti clockwise.
https://www.amazon.co.uk/Irwin-Power-Screw-Extractors-Pieces/dp/B000EF1EHY
- If you have a Dremel/multitool, Dremel a flat head socket into the valve and use a flat head screwdriver. Some people use a chisel but that might be a bad idea…
Once you have the valve out be sure to find a replacement rather than winding the same one back in.
- If your totally stuck, another old trick is to use a Self tapping screw with PTFE wrapped around it.. we’ll leave the standard of your DIY up to you..
Or…
Try the Easibleed solution
Easibleed is essentially a be very careful not to over tighten and watch their vid on youtube before going ahead. Also note that a poorly painted, unevevn or rusted surface of the radiator will leak. Amother warning we received from engineers was too look at Rad panel thickess. If you have particularly thin panel you may need to trim a bit off the end.
Replace radiator! If you’ve tried all the above and still have not joy the thing really does belong in the recycling plant, time for a renewal.
When and Why to Bleed a Radiator
We’ve covered how to do it, but why should you bleed a radiator? There are a few common scenarios when it makes sense to perform this type of maintenance. Here we’ll explain just when and why you should tackle radiator bleeding.
With Brand-New Radiators
A new system might require venting to ensure proper circulation of the system water. Proper pressure is essential for keeping your radiator (and entire heating system) functioning properly. In general, most household heating systems should have approx. 1.5 bar (for two stories). With more stories, however, you might need higher pressure depending where your gauge is located.
When the Radiator Isn’t Heating Up
Let’s say you’ve turned on the heat and are expecting some cozy warmth when you realize it’s still a bit chilly near the radiator. Maybe you feel cold spots specifically at the top of radiator, or perhaps it’s just lukewarm all over. Now is the time to try bleeding/venting—it’s most likely trapped air keeping the hot water from reaching all areas of the radiator. Infact, if you look at a radiator design its essential for air to be in the top section to ensure full thermal circulation, if water does not sit in this top part you will lose around 90% of its output!
Gurgling and or banging in your system
A noisy system can be irritating, especially noisy bedroom radiators. Although this may not be as simple to cure as giving your rads a quick bleed/vent, if it is just a case of some trapped air you may save your self a callout charge from and engineer.
Regularly Each Season
In some cases, bleeding your radiator should become part of your regular maintenance. Think of a rental property before new tenants move in, or a vacation home you don’t live at year-round. Even in regularly lived-in homes, checking up on and bleeding your radiators at the start of the cooler season is a smart idea to keep everything working properly.
Bleeding Radiators for General Maintenance
We mentioned bleeding radiators as regular seasonal maintenance, but what about the rest of the time? In some cases, it’s helpful to bleed your radiators on a more regular schedule.
Benefits of Regular Radiator Bleeding
The simple task of bleeding a radiator might seem like a quick fix for heating issues. After all, you likely ignore your radiator unless it’s not working right! But regularly bleeding hot water radiators has a few benefits, such as:
- No surprise cold rooms
- May indicate a radiator and or your system has a rust issue (more on that later)
- Maintaining proper system pressure
- Stop air being dragged back in to other parts of the system
- Saving energy costs
By keeping all the air out of your radiator you will be able to maximize its potential output. This in turn means you will be able to run at lower and more comfortable temperatures, in turn saving energy. Taking care of cool spots in your heating system will not only lower your energy costs, but it will make your winter more comfortable, too!
How Often to Bleed a Radiator
It’s a smart idea to bleed your radiator at least once per year. Checking your whole heating system at the start of winter is an excellent general plan. But you should also be prepared to bleed the radiators in the middle of the season, too. If you are finding air in the system more than once a year, or anything more than a very small amount of air this may indicate issues of air entrainment or corrosion in the system.
Especially if you notice a drop-in temperature or efficiency, doing a mid-season bleed can help save you money on energy costs. Any time you notice a radiator operating at lower-than-normal efficiency—say heating up slowly or not putting off as much heat as normal—give it a a quick bleed to see if that helps.
Bleeding When Filling a System
A few scenarios will require you to fill your heating system from empty, and in these cases, bleeding is necessary. Whether it’s a new radiator, a new boiler, or an entirely new heating system altogether, here’s what you need to know about bleeding when filling a system.
Bleeding New Radiators
A new system or individual rad will obviously need bleeding or venting to allow the water to fill up the radiator. With a system you should start with downstairs radiators, as getting the air out of those will help avoid issues upstairs (since air rises).
Bleeding Radiators with New Equipment
Installation of new heating components is one of the top reasons to give the radiators a bleed in the first place. But new radiators aren’t the only equipment that will prompt you to bleed the system. If you install a replacement boiler, pump or valve, for example, you may want to check the whole system depending how much was drained and give it another bleed around a week after use.
Keep in mind that even if you install a new boiler or other equipment, there could still be problems with your old radiators. For example, if your radiators require frequent venting, you might have something other than innocuous air taking up space.
In dirty systems, you might notice ‘gassing,’. Instead of air, you’ll have hydrogen off-gassing coming from the system, which happens when there’s corrosion somewhere in your heating system and most likely in that radiator. The only way to test this is to light the gas that is being vented, if it lights the gas is hydrogen and you have corrosion. We however strongly advise against this.
Making sure the entire system is properly cleaned when you install new parts is the first step in avoiding gassing. But you’ll also want to ensure there aren’t any bacteria growing inside, which is what can produce toxic and particularly smelly hydrogen sulfide.
Common Questions
Although it’s a simple procedure, you might have some practical questions about the process. Here are the answers to common questions about bleeding radiators.
Do you bleed your radiators with the heating on or off?
It’s a good idea to turn the radiator off while you’re bleeding it. Apart from potential safety issues if the radiator heats up fully while you’re working, you might even be adding more air into the system by leaving it running.
Most sources recommend turning on the heating system full blast for at least ten minutes before you start working on it. However, if you are working on a high temperature system you’ll want to shut it off and make sure you either wear gloves or just avoid touching the body of the radiator while you work .
Do you have to bleed radiators in order?
You don’t have to bleed radiators in order, but it’s a smart idea! For example, starting with your home’s lower-level radiators makes it easier to avoid pushing air into the upstairs units. After all, air rises, so if you start downstairs, you’re cutting off one source of air for the upstairs radiators.
Why does my radiator need bleed every week?
Some radiators begin to require bleeding more often when they have internal corrosion. If the water appears particularly black while venting the unit, it could mean there’s something else going on other than air buildup, i.e. corrosion.
A radiator can develop corrosion if it’s not cleaned or maintained properly over a prolonged period. You might also notice issues if you’ve replaced some of your heating components (or added a new radiator, for example) but haven’t run a system check.
This is particularly common in bathroom towel rails for 2 reasons. 1) Typically towel rails are made of poor-quality metal, and 2) the design of a towel rail means flow travels left to right rather than up and down. This lowers the velocity of the water meaning air can come out of suspension more easily.
It’s helpful to bleed the system while you’re filling it, to avoid trapping air inside. But you will also want to check each radiator for potential corrosion or other damage before introducing a brand-new component to the system.
As a very general rule, if you see corrosion on the outside of a radiator there is a very good chance there is corrosion on the inside.
Summary
Radiators that don’t heat properly are a huge headache for homeowners. Fortunately for us, it’s possible to bleed a radiator in a matter of minutes, getting the system back up and running quickly.
All it takes is a bit of preparation and some simple tools, and you can DIY a radiator checkup that will help cut your energy costs and make your home comfier and heating system more efficient.
