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Radiator cold at the bottom? Here’s how to fix it

Your radiators should heat up evenly and never have cold patches when your heating is on. If you can feel cold spots on your radiators, that usually means there is a blockage preventing hot water from circulating properly. 

Radiator problems can cause a significant headache, particularly during the coldest months of the year. Fortunately, there is a simple solution to this issue, so you might be able to fix it yourself without contacting a professional.    

If one or more radiators in your home are cold at the bottom, we’re about to explain how you can put them right. 

How to check whether your radiator is working

First, check your central heating is switched on, then make sure your thermostat is not set too high. If you have thermostatic radiator valves, turn them on as well. Once your heating has kicked in, the thermostat is at a reasonable temperature, and your radiator valves are on, you can check your radiators for cold patches. 

You should feel every radiator in your home when checking for cold spots. Make sure you have a good feel of your radiators to determine which ones are not working and whether they are cool to the touch at the top or the bottom. 

If you find your radiators aren’t heating evenly or have cold spots, the likely culprit is a blockage or sludge build-up, so you will need to bleed them. 

How to fix radiators with cold patches at the bottom

If one or some of your radiators are cooler at the bottom, then chances are you need to bleed these radiators to fix the problem. Bleeding your radiators is a quick and straightforward process, provided you know what you’re doing. 

But don’t worry if you haven’t had to bleed your radiators before. You can follow our step-by-step guide on bleeding radiators below. 

1. Switch off your heating

Before you begin, turn off your central heating and wait for your radiators to cool down. If you don’t let them go cold, you could end up spraying yourself with hot water when you bleed your radiators. 

2. Lay down some sheets or towels underneath and around your radiator 

If you have a sheet or towel you don’t mind getting wet or messy, lay it down underneath and around your radiator to protect your floor. Pop another sheet or towel between the radiator and the wall to protect your paintwork or wallpaper. 

3. Grab a bowl and a small cloth or towel

Once you lay down a sheet or towel underneath your radiator, you may want to put a bowl on the floor under the radiator valve to catch any drips of water. You can also hold a small cloth or towel underneath the bleed valve. 

4. Turn off your radiator valves

Close your radiator valves until they are tightly shut.

5. Find your bleed key 

The bleed key fits into the release valve on the side of your radiator. If you can’t find one at home, you can visit any DIY store to purchase one. 

6. Bleed your radiator

Hold your bowl underneath the release valve and then put the bleed key into the valve and turn it anticlockwise. As the valve opens, you will hear a hissing noise, which is the sound of the air escaping. When a steady stream of water starts leaking from the valve, turn the key clockwise. Keep turning the key until the valve is tightly closed. 

That’s it. You’ve finished bleeding your radiator. You can now move on to the next radiator if more than one has cold patches. 

7. Switch on your heating

After bleeding the radiators, you can turn your central heating back on to check whether they are heating up correctly. 

Are your radiators still cold?

If your radiators are still cold at the bottom after bleeding them, then you should contact a Gas Safe registered engineer to identify the cause and fix the issue. They may say your central heating system needs flushing or there is a problem with your thermostatic radiator valves. You’ve already done all you can, so be sure to leave it to a professional to diagnose and repair the problem.