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Why Is Your Radiator Cold At The Bottom?

Why is Your Radiator Cold at the Bottom?

Although your boiler may be in perfect working order, if your radiators aren’t operating properly heating your home can be near impossible. Radiators do not require much in the way of maintenance, but if you’ve never performed any maintenance on your central heating system you can run into problems.

You may notice that your radiators are no longer evenly heating and feel cold patches on them, particularly at the bottom. If this is the case, likely, your house isn’t heating as effectively as normal. Fortunately, there are things you can do to rectify the problem. In this article, we’ll discuss the probable cause for this and what you can do to get your radiators back in working order.

What causes a radiator to be cold at the bottom?

Usually, the reason for radiators to unevenly heat up is due to a blockage. Radiators require water to move freely throughout their inner workings to evenly heat. Often, the blockage that is preventing the water from making its way through the radiator is a form of sludge. Due to the weight of the sludge, it usually sinks to the bottom of the radiator and causes it not to heat correctly by blocking the water entry and exit points.

Although there are several reasons why a radiator isn’t operating effectively, this is the most common reason for a radiator being cold at the bottom.

Sludge in radiator

What causes sludge?

Unfortunately, sludge in fairly unavoidable and without occasional maintenance can cause blockages in your radiators. Sludge forms in the pipes and radiators in your home because of the materials that they are made from. Radiators are usually made with steel or iron, as water passes through this material, sludge can form over time. This is due to the iron oxides that are formed as a result of this process.

Additionally, limescale and deposits of other minerals found in the water can also contribute to sludge build. As sludge builds up, it can cause blockages in different areas of your radiator, which is why cold spots can be felt. The water pressure isn’t enough to shift this sludge and usually, you’ll have to remove it yourself if you want your radiators to function properly.

How long can I leave sludge to build?

If you want your house to heat correctly then your top priority should be to remove the sludge as soon as possible. If left, the sludge can eventually damage your boiler and you’ll be wasting energy unnecessarily, which not only means your house won’t be as cosy as it should be but also means that you’ll have to leave your heating on for longer, which can be costly.

Fixing the problem

Most blockages caused by sludge do not require you to call in professionals. If you have basic DIY skills, you’ll usually be able to remove the blockage yourself. The process can be timely if several radiators are affected, but shouldn’t take too long if you only have one radiator to clear. If you think that all of your radiators are blocked, calling in a professional that will have specialist tools can be a more simple solution.

If you want to rectify the problem yourself, follow this process to manually flush out the sludge:

1. Isolate the radiator by turning your radiator thermostatic valve down to 0 (Some radiators won’t have one of these). Locate the lockshield valve, which is usually on the opposite side of the radiator and will often be covered with a plastic cap. Close the lockshield valve with a spanner.

2. Put several towels down below the connector nuts and loosen them slightly as well as a bucket or large bowl to collect water as you bleed the radiator. When you loosen the connector nuts, you may notice some discoloured water leaking out, this is normal.

3. Use a bleed key to open the bleed valve at the top of the radiator, this will allow air into the radiator which will flush out the water through the connector nuts for you to collect in a bucket.

4. Once you have drained all of the water from the radiator, undo the valves the rest of the way and remove it from its wall brackets and take it to an outdoor space.

5. Attach a garden hose to one end of the radiator and flush water through it. You’ll notice the sludge dislodge and colour the water. Keep flushing water through until the water runs clear.

6. Once you’ve finished, take the radiator back inside and reattach it to the wall and then to the pipes and reverse the process from step 1. Be sure to close the bleed valve as soon as you start seeing water appear from it as the radiator will fill with water as soon as you open the valve.

7.Your system should repressurise itself, but you may need to add more water and build up your pressure manually. Check your boiler’s pressure gauge to determine whether this is the case.

Michael Cornish