Common Underfloor Heating Problems; The Complete Guide

Underfloor heating installations are high quality, robust, and long-lasting compared to radiators, but problems can occur. Understand what causes the most common underfloor heating problems, and what you can do to avoid them.


What Causes Problems in Underfloor heating?

Poor design and poor installation quality are the primary reasons that many of the issues outlined here develop in a short timeframe. Of course, some faults occur naturally across the lifespan of the system, and this can be prevented through good maintenance and annual checkups. With EasyFlow, your installation has a 2-year workmanship guarantee, and we will cover you if any faults occur within in that time. If you had another provider install your heating, be sure to have any records of a warranty or guarantee on hand.

One of the benefits of underfloor heating is that the majority of issues are localised to the manifold, boiler, or thermostat. It makes searching for issues much easier. Not to mention, the process of prevention through good maintenance is simplified.


The Floor Isn’t Heating

How underfloor heating works on a technical level is that a thermostat sends a signal to the manifold when a room drops below the desired temperature. The manifold then sends a signal to the boiler, the circulation pump, and the actuator to begin the flow of hot water. A problem with one of these components can affect the distribution of heating across your home.

First, we need to diagnose if it is a single zone that is affected, multiple, or all zones. If multiple zones are impacted, are they controlled by one or more thermostats? From there, we can begin diagnosing the potential causes.


A Single Zone Isn’t Heating Up

This is most likely to be an issue with the thermostat not sending a signal to the manifold. It can also be an issue with an air bubble, or the actuator, preventing water from getting into the zone. The following procedure will help you narrow down the issue.

  1. Isolate your underfloor heating installation to the faulty zone alone.
    • If the boiler is still running, this is indicative of a failed/faulty actuator or an air bubble blocking the system.
    • Check the pin valve near the actuator. If it is stuck, use nose pliers to free it
  2. Check your thermostat for any error messages, change the battery if it is low, or reset it according to your user manual.
    • If you receive an error code, follow the troubleshooting instructions in the thermostat manual and seek help from the manufacturer if necessary.
  3. If you are still experiencing problems, check with a professional experienced in underfloor heating thermostats and wiring boards.


Multiple Zones Are Not Heating Up

Refer to the previous section if one thermostat controls these zones. If they use multiple thermostats, then this is most likely the failure of a component on the manifold. If other zones are still heating up. 

  1. Isolate your underfloor heating to only the faulty zones.
    • If the boiler is still running, there is a blockage or actuator issue.
    • Check the pin valve near the actuator. If it is stuck, use nose pliers to free it.
  2. If the heating stops running, check your thermostats for any error messages.
    • Change the battery if it is low, or reset it according to your user manual.


All Zones Are Not Heating

If you have multiple zones controlled with multiple thermostats, and all are not heating up, this is indicative of a blockage before or in the manifold, an issue with the boiler, or the failure of a manifold component. The following procedure will help you narrow down the issue, but the majority of these will need an experienced heating engineer to fix.

  1. Check if the boiler is running at an adequate pressure.
    • Low pressure is indicative of a leak in the system.
    • If it is not firing, there may be a problem with the manifold wiring connections or power supply
  2. Check if the main isolating switch supply is turned on
    • If off, there is no power being supplied to the wiring board.
  3. Check if you can hear a whirring noise from the circulation pump
    • If you cannot hear a noise, a mechanical or electrical fault is causing it to fail.
  4. If it is none of the above, it may be the fault of another manifold component, such as the actuator or mixing valves.


My Problem Happened Because of an Airlock. Are Underfloor Heating Setups Supposed to be Airtight? Do I have a Leak?

Heating systems naturally take in a very small amount of air and lower in pressure slowly over time. The older the components, the more likely this is to happen. An air vent placed at the highest point of the manifold helps remove air when it does get into the system. If this is a recurring issue, having your boiler engineer run an air escape cycle on your boiler during its annual service will help remove air bubbles between the boiler and the manifold.

Air likes to settle at the highest parts of the network, and you typically see large airlocks in points of elevation (piping going upwards, over the boiler or the ceiling).  This is a poorly designed system if there isn’t anything in place to help the air escape from these problem areas. 


The Floor Isn’t Reaching the Desired Temperature

If your floor feels a little colder than it normally would, it isn’t always a cause for concern. Your thermostats will communicate with the boiler, indicating what the flow temperature should be. If the floor only requires a little warming, it may not heat all the way. Of course, there can be other reasons, and the following procedure can help you diagnose this.

  1. Check the flow temperature reading on the boiler, then on the manifold.
    • If there is a dramatic difference, there may be a problem with your boiler’s temperature sensor.
  2. Check the boiler pressure as the system starts up.
    • If it low or fluctuating, you may have a leak, air bubbles, dirty water or sediment interfering with heat transfer.


Pressure Issues on the Boiler

Pressure slowly decreases over time. If you notice sudden increases or drops in pressure, it means something isn’t right. The most likely cause being a leak and subsequent air bubbles in the system. These are most likely to occur in the pipes between the boiler and the manifold. If you have an underfloor heating installation that does not run in continuous loops, then you may have joints or breaks elsewhere in the heating system letting air in and water out. 


Sudden Pressure Drops

  1. Check for leaks around the metal pipework, pressure valves, air vents, and boiler blow off valve.
  2. If you still cannot detect the leak, repressure the system, then isolate the manifold.
    • If pressure drops on the boiler side, it is a leak in that part of the network.
    • If pressure drops on the manifold side, it is a leak in the pipe network.


How do I find a Leak in the Pipe Network?

A leak in the underfloor pipes will lead to discoloured or damp patches in your Gyvlon screed or leveling compound. This may be difficult to detect with a floor covering, so a moisture detection metre may be necessary.


Sudden Pressure Increase

  1. Check that the water filling loop is sufficiently closed and not pushing more water into the system.
    • If this is the case, close the filling loop and let water out of the drain-off point until pressure is at a safe level.
  2. Carry out pressure testing if you are confident and experienced to do so.
    • If the pressure fluctuates, this could be a faulty pressure sensor in the boiler, dirty water, or air bubbles present in the system.
    • If pressure stays high, it may be a fault inthe expansion vessel.
  3. Depress the needle in the valve of the expansion vessel to check its integrity.
    • If water comes out, the vessel has failed and requires replacement.