What makes my radiators knock, bang and leak?

problem radiators

In our previous blog we explained how a central heating system works and how to remedy a cold radiator. Recapping a Central heating system is a very simple structure. A boiler (fuelled by gas or oil) is the most important part of a central heating system. Imagine a boiler as a big fire with a continued supply of fuel. When a boiler is switched on the gas or oil enters a sealed combustion chamber and via an electric ignition system the fuel is set alight. A heater exchanger connected to a cold water pipe is then infused with fine jets of heat (around 60°C/140°F) which in effect heats the water. This heated water is then moved along the pipework system (usually hidden in newer homes) by an electrical pump. Within your home when your heating system is on there is a continuous flow of hot water within pipework.

What makes my radiator knock?

Knock, knock – different radiator noises often have different causes and require different solutions – all can easily be fixed yourself:

Whistling This is caused by the water flow rate. A whistling noise usually indicates that water is flowing through the radiator too high. This can be solved by turning the radiator valve to full.

Ticking A ticking radiator is completely normal and needs no attention, this is just the radiator warming up or cooling down.

Tapping This is usually caused by an incorrectly fitted thermostatic radiator valve. The problem may be that the valves have been mistakenly switched (especially if you have just had a new radiator fitted).

Why does my radiator make a banging noise?

A banging noise from your radiator is now less common than it was 20 years ago. There are three main causes of banging:

Trapped air The best way to solve trapped air bubbles in your radiator is to bleed it. You may have to do this a few time over the course of a few hours/days to get all the air out. If the problem persists consider using an autovent valve. An autovent valve continuously removes air from your radiator as hot water is circulated around the central heating system.

Expanding pipes When a central heating system is on, hot water is being pushed along the pipework. As pipes heat up they expand. As a pipe expands it may warp and move (very slightly). If a pipe is resting against something hard this will cause a noise. If the object the pipe is resting on can be moved (such as an item of furniture) we could recommend moving your furniture a fraction or installing a foam pad.

Limescale In hard water areas limescale builds up in the boiler’s heat exchange system and constricts the flow of water. As the pressure builds up, water turns in to steam, when these steam bubbles collapse and turn back in to water you get a rumbling/banging sound.

Why does my radiator leak?

If your radiator shows no sign of corrosion, dry the radiator to enable you to identify where it is leaking from.

Is the leak coming from a valve or stop cock? It may be that you need to tighten or replace the valve. Adding some PTFE tape (thread seal tape) may give you some extra peace of mind.

A leak at the coupling nut can often be fixed by tightening this. Click on this link to see great demonstration of how easy this is to fix.

Is the leak coming from a spindle? Tighten the gland nut within the spindle. If this does not work, you might have to call in an expert.

If your radiator has corroded with age this could be causing it to leak. Unfortunately, you will need to replace the radiator.

Please don’t attempt to touch any part of your boiler or central heating system if you’re unsure or not confident. Do not use a gas appliance if you think it’s unsafe.

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