Node connecting floor heating system to hot water supply

Key takeaways

  • Water underfloor heating provides warmth to a home from hot water rushing through pipes below a property’s surface.
  • Flushing is the process of removing any contaminants such as debris and sediment, to enhance the operations of a wet underfloor heating system.
  • To prepare for flushing, you need the right equipment and must put precautions in place to ensure your safety.
  • Flushing the system is a step-by-step process that includes turning off your underfloor heating, cleaning, refilling, and bleeding it.
  • Contact Next Level for help with flushing your underfloor heating system if you can’t do it yourself.

While an underfloor heating system provides high levels of comfort and efficiency, its longevity and smooth functioning require regular maintenance. Flushing is one of the most important forms of maintenance, but homeowners often overlook it.

Flushing is the process used to clean any underfloor heating pipe and the manifold system due to any debris that accumulates over time, making the system perform inefficiently. Therefore, we've put together this extensive guide to provide you with all you need to know about this maintenance procedure.

Keep reading to discover more about flushing a wet underfloor heating system, including general steps, troubleshooting, and preventative maintenance.

The ins and outs of underfloor heating

In general terms, underfloor heating is a form of central heating system that warms up an entire room or home by generating heat from below the surface of the property. There are two main types of underfloor heating systems:

Wet underfloor heating system

A wet, water or even hydronic underfloor heating system is arguably one of the most sustainable methods of providing warmth to a property. It involves installing a series of pipes or tubes below the surface, which are attached to a manifold. When turned on, hot water will flow through these pipes, eventually generating enough warmth that it moves through the floors and keeps a room feeling comfortable.

Electric underfloor heating system

An electric underfloor heating system works with the same comfort as the former, but the components are different. Instead of installing pipes and tubes, a series of cables or heating mats are placed below the flooring. It uses electricity instead of water, and due to this, it's recommended that this sort of system be used for smaller rooms instead of larger surface areas to save on energy.

When it comes to power flushing an underfloor heating system, you only need to focus on a wet underfloor heating system. Since the electric system doesn't use water, it is maintained in other ways that don't involve a power flush.

The importance of flushing wet underfloor heating

Collage showing before and after installation of floor heating system in a house

What is flushing?

Flushing is a complete contamination removal process. Sediment and debris created within the system, in addition to foreign particles and air pockets, reduce the efficiency of the underfloor heating system, causing uneven heating and leading to potential malfunctions.

Flushing, however, eliminates all contaminants completely, maintaining an uninterrupted heat distribution cycle and the highest possible efficiency. Flushing, performed with a cleaning solution, includes draining the system, circulating the solution, and rinsing to remove all remaining residue. By maintaining the system’s efficiency and effectiveness, flushing also increases the lifespan of the entire system.

Common issues caused by neglecting flushing

Neglecting power flushing in underfloor heating systems can lead to several common issues, including:

Reduced efficiency

Accumulated debris and sediment restrict water flow, increasing the amount of work the system has to do to achieve the desired temperatures. This leads to increased energy consumption and reduced efficiency.

Uneven heating

Buildup in the pipes leads to blockages, which in turn causes the uneven distribution of heat across the floor surface and cold spots in the different zones of the system.

System failures

Sediment buildup can cause corrosion and damage to such components as valves, pumps, and manifolds, ultimately breaking down the system and requiring expensive repairs.

Increased energy costs

Sediments force the wet underfloor heating system to work harder, which increases overall energy costs.

Comfort issues

Inadequate heat distribution may cause some areas to remain too cold while others are too warm, making the system inefficient and uncomfortable.

Reduced lifespan

Underfloor heating without proper flushing can make the systems last much shorter than expected, resulting in premature replacements and urgent repairs.

Frequency of flushing required

The recommended flushing frequency for underfloor heating systems depends on several factors, including the quality of water, the frequency of system usage, and environmental conditions. Flushing the system every 1 to 3 years ensures that no sediments accumulate inside and that it always works to its best ability.

However, annual or bi-yearly flushing is recommended if you live in an area with hard water, as this can lead to a large amount of sediment.

You can determine how often you need to flush your system for sure based on the results of regular inspections and performance control. By following these recommendations, your underfloor heating performance will be at its highest for a long period, and you will extend its overall lifespan.

Preparing for flushing

Before you start power flushing your water underfloor heating system, you need to do a few things to get ready first:

Tools and equipment required

  • Drain valve key: Opens and closes the drain valves, allowing drainage from the system.
  • Hosepipe: Used to connect the drain valve at the boiler, allowing water from the system to be flushed.
  • Pump and hose: The circulation pump and a hose are required to circulate the cleaning solution around the system.
  • Cleaning solution: A suitable cleaning solution for flushing underfloor heating systems.
  • Bucket or container: A bucket or container used to collect flushed water and other debris during the process.
  • Pressure gauge: A gauge used to monitor the system pressure during the flushing and refilling.
  • Bleeding key: Used to bleed the air from the system after flushing and refilling.
  • Pipe cutter or tubing cutter: In case pipes need to be cut while undergoing repairs or maintenance.
  • Safety gear: Gloves and eye protectors to ensure safety while working with the chemicals and the equipment.

Safety precautions

While you want your underfloor heating system to operate at the highest quality, you still need to put your own safety first. Here are some of the top precautions you should put in place:

  • Ensure you turn off the power supply to your wet underfloor heating before doing anything else. We'll tell you how to do this in a bit.
  • Always wear the safety gear we mentioned above. It is there to help protect your eyes and hands and prevent the opportunity of injury.
  • Don't flush your system with all the windows and doors closed. You should ensure the area is properly ventilated to stop the build-up of fumes from the cleaning solution.
  • When using cleaning solutions, look at the instructions to ensure you're using them safely and in the right quantities.
  • Beware of hot water during the power flushing process. If your underfloor heating system hasn't cooled down, you might be prone to developing burns.

Shutting down the system

As we previously mentioned, you must turn off your wet underfloor heating systems before you even think about starting to flush the system. This is because having it on could lead to accidents and injuries, and your safety is important.

Simply follow these steps:


Locate the main panel to which your underfloor heating system is attached and turn off the power supply.


Shut off the flow of water throughout the pipes in your system by closing the isolation valves on the supply and return underfloor heating pipe.


Wait some time for the system to cool down. You don't want the water to have any heat in it before you start flushing or any other maintenance to avoid burns.

Step-by-step guide to flushing wet underfloor heating systems

Collage depicting the process of professionals installing floor heating

Once you've got all your equipment and put all your precautions in place, you are ready to start with your power flush.

Go through these steps with precision for the best results:

Draining the system

The first and most fundamental step in flushing the underfloor heating system is draining the current water. Locate the drain valves on the heating system's supply and return pipes. These drains have hoses attached that help channel the drained water away from the heating system.

Use a drain valve key to open each valve and allow the water to flow fully. You must be patient while thoroughly draining all the water during the drainage process. All the water should be drained from the system before any other maintenance procedures occur.

Cleaning the pipes and manifold

Once the underfloor heating system is drained, the pipes and manifold should be cleaned to eliminate the accumulated sediment and debris. First, the pipes and manifold should be inspected for any visible contaminants and clogs that can be flushed out or physically eliminated. Next, a cleaning solution recommended by the manufacturer should be used to dissolve and remove deposits efficiently.

The pumping equipment can circulate the cleaning solution through the pipes using a hose to ensure all surfaces of the pipes and the manifold are cleaned. The solution should be left in the pipes for an appropriate amount of time to achieve the best results. The pipes and manifold should then be thoroughly flushed using water.

Flushing with a cleaning solution

Power flushing your underfloor heating system with a cleaning solution is essential to eliminate stubborn sediment and sludge. Firstly, you should prepare the cleaning solution as recommended by the manufacturer of your system or an expert at Next Level.

Next, attach the pump and hose and circulate the cleaning solution in/and out of the pipes, ensuring it reaches the manifold. This allows the solution to flow in the pipes and breaks down the dirt. You will also need to keep checking on the solution as it flows and adjust the circulation if necessary. Finish off by rinsing the system with clean water, ensuring all the dirt is removed.

Refilling and pressuring the system

Refilling and pressurising is the most appropriate method to restore your wet underfloor heating systems' functionality. This process starts by closing the flushing equipment and the system’s drain valves, reconnection and turning off the water supply and re-filling with clean water sources to remove air pockets.

It is accompanied by the constant observation of the pressure gauge to refill the system and maintain the optimal indicators, as well as the use of the bleeding to remove air and prevent airlocks. The process ends with a check for possible leaks and repressurisation. Refilling and pressurising water helps restore the system's optimal operation and efficiency.

Bleeding air from the system

Air bleeding from the underfloor system is essential to enable proper flow and eliminate air locks. The system’s first step involves finding the bleed valves commonly positioned on the manifold, often the system’s highest point. To achieve this, each valve is slowly opened one after the other by inserting a bleeding key starting from the farthest point from the pump.

When air is released, a hissing sound is produced as water flows out. Keep bleeding until water flows consistently on each valve without bubbles before closing the valves tightly. This process is essential as it eliminates possible challenges and keeps the heating efficient.

Preventative maintenance tips

Preventative maintenance is critical for underfloor heating systems' proper operation and longevity. The following are some important maintenance tips:

  • Regular inspections should assess the pipes, check any accumulations, and detect leaks, damage, or any visible degradation signs, including pipes, valves, and manifolds.
  • Add proper inhibitors to freshwater to stop corrosion or mineral staining within the system.
  • Avoid sudden temperature changes, weakening the system and reducing efficiency.
  • Keep the area around the manifold and heating elements clean to enhance efficiency and use them as intended.
  • Hire a certified technician to conduct routine maintenance checks to ensure the system operates and all parts work efficiently.
  • Invest in an efficient energy monitoring system to monitor your energy usage and spot potential complications or upcoming issues.
  • Reorganise the system based on seasonal work to maximise energy value and optimise comfort.


Underfloor heating can bring many benefits to a home, such as replacing another central heating system and offering energy efficiency and year-round comfort. However, you can only do this if you continue to maintain your system and conduct regular power flushing. If you need any help doing so, then Next Level has the experts to help. Contact us today, and we'll be able to help you remove cold spots or simply keep your system running smoothly.

Completed installation of floor heating system in a house

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