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Why are my radiators cold at the bottom?

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People normally place their hand on the top section of the radiator to find out if their heating is operating properly. This is not the correct way to find out if your radiators are functioning efficiently. To better grasp the idea, turn on your heating for 30mins, put your hand around the middle lower part of the radiator and you should be able to feel the difference in temperature. You will also notice the radiators furthest away from the boiler will have larger cold sections.  

What prevents the bottom of the radiator from heating?

Two reasons why your radiators don’t heat at the bottom, the first is Poor flow rate. Radiators function by moving heated water in one side and out the other. If enough water is not pushed through the radiator, then the middle lower section cannot heat. The second reason is high delta t, this is the temperature differential between the radiator inlet and outlet, which is 11°C in the existing system (11° Delta t). High temperature loss across a radiator panel indicates slow heat transfer. In a situation like this it is only a matter of time before the cold section of the radiator gets larger, due to corrosion and build- up of silt.      

How can I fix it?

The most common answer you get is to flush out your radiators. As the logic is, a radiator that is cold at the bottom usually have something obstructing the flow of water. Flushing radiators is an expensive process and does not guarantee results, it is a short term solution to a reoccurring problem.

The system you have in your home operate on an average flow rate of 1.5 Litres per minute for each radiator. It has an average 11°C heat drop between inlet and outlet temperatures across all radiator panels. The radiators furthest from the boiler are the ones most effected. This is one of those problems that you cannot fix yourself. As a Plumber myself I too had to walk away from radiators not heating as there simply was no product or solution on the market to fix them.   Hence the development of Oxyvent.


The Oxyvent system increase the flow rate to your radiators from 1.5 Litres per minute to 3.5 Litres per minute, and has a temperature drop of only 2° across the radiator panel. By moving extra water through all the channels in the radiators the complete panel heats up. As the top and bottom of the radiators are at a more uniform temperature, more radiant heat is given off the front panel which create higher temperatures at floor level. Oxyvent give you more comfort for less fuel.

Contact Oxyvent and heat the full radiator panel.