During the winter months there is nothing worse than coming home after a long day at work, wanting nothing more than to settle down with a lovely warm cuppa only to find that the house is cold. The first thing we all check is whether we set the timer right on the boiler, then we check the thermostat and then the boiler itself, hoping beyond all hope that it hasn’t broken down. They all seem ok but the radiators are still cold, so what is going on? If you feel from top to bottom of your radiator, it is most likely that the pipes to the radiator are hot, the very bottom of the radiator is warm and the top cold. If this is the case there are potentially two things going on: If you have them, it could be that the thermostatic radiator valve has failed and is not opening or it means that the radiators need bleeding. In this guide we will walk you through why this happens and how to get your radiators working again.
Thermostatic Radiator Valves (TRVs)
TRVs are installed on radiators to specifically control the temperature in the room in which the radiator is located. They open and close based on the air temperature in the room and if they fail, they could fail in the closed position preventing hot water flowing around the radiator. The easiest way to check is to just screw off the thermostatic head which will then allow the valve itself to open. If you have done this and the top of the radiator is still cold, then it is likely that there is air in the radiator reducing the amount of hot water than can flow through and significantly reducing the heating power of the radiator.
What causes air in radiators?
Air can be present from when the radiators were first filled, if it is new system, but for older installations air typically gets in through either small leaks in the system or simply through the natural expansion and contraction of the system over time which causes small bubbles to form. Over time these collect in the high points of the radiator to form an air lock which then stops water from flowing and that leads to the cold radiators and your cold room.
How to bleed a radiator
Thankfully this is extremely simple and will fix the issue with the radiator being cold immediately. Make sure that the boiler is off and the water cold. Yes we know this is a faff, but you don’t want hot water under pressure blowing out of your radiator. At the top of the radiator on one of the sides there will be a small square nut. Some have a slot for a screwdriver and some don’t. For those that don’t you will need a radiator key, which are available online or in any DIY store. Get yourself some towels or rags and you are ready to go. Wrap the towels around the valve and under the radiator. Water will spray out and you want to protect your walls and flooring. Gently unscrew the nut. Don’t go too fast or too much or you might end up squirting water everywhere or even worse totally unscrewing it causing it to fall out, which will be a very wet adventure. You will hear some hissing if there is air in the radiator and simply allow this to release until you see water appear. Now close the valve, the radiator has been bled. Make sure to close the valve properly or it could leak. Do this for all your radiators. Once you have bled all the radiators, you will need to go and check your boiler pressure as there is every chance that the bleeding process has caused pressure loss which will cause a fault on the boiler. If the pressure is low, use the filling loop to re-pressurise the boiler. Once that has all been done turn the boiler back on and go back and check all the radiators. If air in the radiator was the issue, it should now be resolved and you can look forward to a lovely warm home.
Radiators really shouldn’t need to be bled more than once a year, if they need bleeding regularly it could be a sign of a bigger issue with the heating system which will need to be checked out by a plumber.
