Heating · 4 min read
Radiator Not Heating at the Top? Here’s What to Check
A radiator cold at the top usually has trapped air. Here’s how to bleed it safely, check the boiler pressure and know when to call for help.
Why is the top of the radiator cold?
For radiator repair Bray homeowners can often start with a simple check. If a radiator is warm at the bottom but cold at the top, trapped air is the most likely cause. The air collects at the highest point and stops hot water filling the whole radiator.
This is different from a radiator that is cold at the bottom. Cold patches along the bottom can point to sludge or debris in the heating system.
Radiator repair Bray checks around the house
Turn the heating on and carefully check the radiators around the house. If just one radiator is cold at the top, it may only need bleeding.
If several radiators have the same problem, there may be air throughout the system. Repeated air build-up can also indicate a leak, a pressure issue or another fault that needs investigation through boiler servicing and repair.
How to bleed the radiator
Switch off the heating and allow the radiators to cool. You will need a radiator key, a cloth and a small container.
Place the cloth and container below the bleed valve at the top corner of the radiator. Insert the key and slowly turn it anticlockwise. You should hear air escaping.
Do not remove the valve completely. Once water begins to come out steadily, close the valve gently by turning the key clockwise. Wipe away any water and check that the valve is not dripping.
Take care, as radiator water can be hot and may stain floors or walls.
Check the boiler pressure afterwards
Bleeding radiators can lower the pressure in a sealed heating system. Check the pressure gauge when the system is cool and follow the pressure guidance in your boiler manual.
If the pressure is too low, the system may need to be topped up. The correct method depends on the boiler and heating system. If you are unsure, do not start turning valves at random. Ring an RGI-registered heating professional for advice.
Turn the heating back on
Once the radiator has been bled and the system pressure checked, turn the heating back on. Give it time to warm up, then carefully feel whether the heat is reaching the top.
If the radiator is still partly cold, the issue may involve a stuck valve, poor system balance, restricted circulation or sludge. A general plumbing check can help identify the cause.
When to call a heating engineer
Arrange a proper radiator repair Bray check if the radiator keeps filling with air, the boiler pressure repeatedly drops, water leaks from the bleed valve or several radiators are not heating correctly.
A recurring problem should not be treated as something that simply needs regular bleeding. Finding the cause can prevent further trouble with the heating system. You can also read about the signs that a boiler may be failing.
If your radiator is still cold at the top or you are not comfortable bleeding it yourself, call Gerard at Radiant Heating & Plumbing on 087 212 0814. We provide radiator repair in Bray, North Wicklow and South Dublin, and you can request a written price.
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