Fix a Towel Radiator That Keeps Filling with Air

Over time, trapped air can build up inside radiators which can cause them to have cold spots, mostly the top part of the radiator.  Towel radiators fitted in bathrooms seem to keep filling with air more often than others.  So here, we will look at what can be the cause and what, if anything, you can do about it.

Why do towel radiators keep filling with air?

Air gets into the system when there is a leak, especially if the towel rail is the highest point on the central heating system.  The main way for air to get in is by a hole in the system that leaks water which then allows the pressure around it to push air in.

image of a towel radiator keeps filling with air

Radiators keep needing bleeding combi boiler

When your radiators are not performing well, they don’t feel hot all over even when the central heating is on full. The simple test is to feel the radiator at the bottom, along where the pipe comes into it, and as you move your hand further up, it starts to get colder. By the time you get to the top, it’s really cold. The reason for this is you have trapped air which needs to be bled out.

A sealed pressurised heating system means it is not always possible to vent every air pocket within it after commissioning, so air rises to the highest point on the heating system which can often be a towel radiator

Bleeding a sealed system usually removes the majority of the air but not all.  The most cost effective way to remedy this would be to have an auto-bleed valve installed so you don’t need to manually bleed it every time.

To test if it is a leak, turn off the heating and let it cool completely, then bleed all of the radiators, not just the towel radiator, starting with the furthest away.  Check the pressure gauge on the boiler is at or around 1 bar after bleeding each radiator. 

You can do this process twice and if the towel radiator is still doing the same thing, it probably is a leak.

Where is the bleed valve on a towel radiator?

The bleed valve on a towel radiator is located at the top and can be either on the left side or the right. Most are square-shaped to fit the radiator valve key and usually have a slot or notch in it so you can turn it using a flat screwdriver.

Air in radiator after bleeding

If there is air in a radiator after bleeding, this indicates there is inadequate pressure in the central heating system. The air will need to be released so the radiator can heat up properly. After bleeding, pressure tends to fall so the system needs to be repressurised, you may have to do this up to 3 times. This way, water fills up the system rather than air.

A fix for a towel radiator that constantly needs bleeding

If after checking other radiators in the system, the best fix would be to purchase a towel rail made from better material, such as brass or aluminium with a chrome finish which although costs more, will give a better performance and work to reduce effects of trapped air inside them.