A malfunctioning heating system can throw the household into coldness, causing complete chaos. Therefore, it is crucial to know about some common underfloor heating problems to identify and resolve them timely.

This guide includes signs indicating that the heating system is not working appropriately and the possible reasons behind it. Moreover, this article also discusses some checks that can be performed to analyse the heating system’s condition and how to prevent such problems.

What Are the Signs Which Indicate a Malfunctioning Heating System?

The following are some of the tell-tale signs which indicate that there is something wrong with your underfloor heating system:

Mechanical Wear and Tear

A few moving parts of the underfloor heating system are present beneath the floor, which can be subjected to wear and tear over the years. Therefore, if you feel the floor is too hot underfoot or some spots are not heating up, it indicates potential problems with the heating system’s mechanical parts.


The underfloor heating system operates silently, but if you hear any banging, clicking, or gurgling noise inside your property, it indicates there could be a problem with the system. Such as, if you can hear the water running through the pipes, it indicates an obstruction like an air bubble.


If you feel any gas or flue smell inside your property, it indicates that the heating system is not functioning correctly or any parts have been damaged.

Underfloor Heating Not Working

Why an Underfloor Heating System Malfunctions?

There can be different reasons why an underfloor heating system does not work efficiently. The following are some of the typical reasons which you can diagnose and fix to resolve the issue:

Problematic Pipes

Primarily, an inefficient heating system is the cause of problematic pipes. Therefore, to resolve the issue, you should check for any blockage or trap in your wet underfloor heating system pipes.


Blockages can occur in the underflooring heating system if anything gets stuck in the flue vent outside your property. This blockage can result from accumulated debris, leaves, or twigs, which should be removed immediately. Moreover, you should check for ice blockage in the discharge pipe on freezing days of winter to melt the ice with the help of some antifreeze and make the heating system fully functional.

Trapped Air

It is one of the most common problems that make an underfloor heating system malfunction. If air gets trapped in the pipes, it impacts the system, including the radiators. The trapped air can be removed by bleeding the system where all the valves are opened to allow air and some water to get released from the pipes. The pipes can also be cleaned, and air can be flushed out simultaneously by flushing water through the pipes.

Moreover, this issue can be prevented from occurring during installation. For this purpose, you should flush hot water through the system’s pipework to ensure it flushes quickly and prevent the formation of air bubbles.


If the underfloor heating system’s pressure continues to decrease, it indicates a leakage somewhere. The leakage can be caused due to any damage caused during installation. In this case, you should follow the guidelines provided by the manufacturer to increase the pressure. Moreover, you can also check the connecting pipes and manifold to see if they are in place and if there is no leakage.

Incompatible Flooring

Your flooring might suppress the heat and prevent it from flowing through adequately if it is incompatible with the heating system. This problem can also lead to underground heat build-up with no way to get released, which can damage other parts of the system; therefore, it must be resolved immediately.

To avoid such issues, ensure your flooring material has a TOG (Thermal Overall Grade) rating of less than 2.5 to allow better heat transfer. You should also check the flooring’s thermal conductivity before installing your heating system.

Incorrect Setup

An incorrect setup of an underfloor heating system can lead to several issues that can reduce its working efficiency and make it entirely non-functional in the long run if the issue remains unaddressed.

Screed Damage

Laying screed over the piping work can damage its working efficiency if the pipes are under pressure or full of water. It obstructs the piping system, and hot water struggles to pass through. Therefore, cool water must flow through the pipes when the screed is being laid, cured and set without the pipes being heated due to hot flowing water.

Incorrect Control Settings

Although no significant destructions are associated with incorrect control settings but, if the system continues running with the wrong setup for a long, it can develop significant issues. For this purpose, you should regularly check that the thermostat regulates the boiler’s heating temperature efficiently.

Underfloor Heating

What Checks to Perform?

You should perform the following checks if you feel the underfloor heating system is not working properly:

Towel Test

To perform the towel test, you must have a large bath towel folded up several times. You should place this towel over a particular section of the floor that you think should heat up. Then, set the temperature to 30°C, observe the flame icon on the screen and hear the clicking sound of the thermostat once the heating mode gets switched on.

If the floor under the towel heats up after almost 15 minutes, it indicates that your heating system is working as efficiently as it should. Then, remove the towel and allow the room to heat up for some time. The floor of a well-insulated small room should take about 30 minutes to get warmed up but it can take longer to heat if there is no insulation.

You should visit the room after a couple of hours, and if the floor is warm, the heating system works efficiently. Otherwise, there can be a heat loss issue for which you need to consult your installer to identify the cause of the problem. The heat loss issue can be resolved by installing a supplementary heater or removing the flooring and heating system to reinstall it with better substrate insulation.

Insulation Check

The underfloor heating system gets on when the surrounding temperature decreases and comes below the set temperature. It is done with the help of a temperature sensor which measures the floor temperature and regulates the thermostat switching. The heating system does not operate efficiently if an insulating material, such as a dog bed, mat, or rug, covers this temperature sensor.

As a result, the floor tends to heat up quickly and for a longer time due to thick insulation, due to which the sensor switches off the heating before the entire floor gets warm up. Therefore, you should immediately remove the insulating objects to allow the floor sensor to record accurate temperature for the entire floor to warm the whole room. It will also help to conduct heat away from the pipes into the floor.

Temperature Sensors Check

The temperature sensor is a significant part of underfloor heating as it directs the system when to switch on or off. It is a small black bead present beneath the display of the thermostat. Check the sensor to ensure that it is not damaged, covered or pushed into the thermostat to ensure its accurate functioning.

You should also check the floor temperature sensor with the help of a test meter. For this purpose, you will have to turn off the electrical supply, pop the display of the mounting plate, and undo the mounting screws to release the thermostat from the wall. Then, you should loosen the sensor terminals to remove the wires and clip all the sensor wires to your test meter with the help of clip leads. After that, you should turn on the meter and set its ohm setting to the expected resistance value. If no resistance reading is displayed on the meter, it indicates the sensor is damaged.

All these checks should only be performed if you are an expert with the electrics, otherwise, you should call an expert electrician to conduct all the checks and tests to analyse your heating system’s condition.

Thermostat Check

If your underfloor heating system is not working properly, you should check the thermostat settings. This check also includes checking if the floor probe is properly connected to the thermostat to make the system completely functional. You can consult the user guide that comes with your heating system to reset a thermostat.

System Pressure Check

A properly functioning heating system normally operates at a pressure of 1 to 2 bars. You should check the pressure gauge on the manifold’s flow bar to record the pressure value.

Water Colour Check

You can check the colour of the glass pipes, and if they are very brown or dirty, it indicates the built-up sludge in the system. In this case, you need to flush and re-dose the system with an inhibitor.

Underfloor Heating

How to Prevent Underfloor Heating System Problems?

Regular inspection and maintenance of the underfloor heating system can help you identify potential problems earlier and avoid the issue of complete breakdown. You can take the following measures to prevent different problems which can make the heating system malfunction:

Insulating Pipes

During cold days of winter, water in external pipes can freeze, forming ice which expands and splits the pipes. Therefore, insulating all the heating system pipes is essential to avoid the issue of ice formation and pipe damage.


You should regularly service your heating system at least once a year to ensure there are no leaks, system pressure is correct, and water flows through the pipes efficiently. Investing in an annual service might cost you a few pounds, but it is worth it if you consider the repeated repairs or replacement costs.


The underfloor heating system is robust and designed to stand the test of time, lasting several years, but problems can occur anytime. Therefore, it is essential to identify the minor problems so they cannot get worse and can be resolved quickly.

Regular flushing through the underfloor heating system and ensuring proper insulation of external pipes can prevent many issues from occurring in the first place. Moreover, you should also ensure to get the heating system serviced regularly to avoid major breakdowns.