Home generalVent underfloor heating - that's the way it works!

Vent underfloor heating - that's the way it works!

  • Costs and specialist company
  • Shell construction and ventilation
  • Instructions - Vent underfloor heating
    • 1. Close the flow and return
    • 2. Connect main distributor
    • 3. Connect the return manifold
    • 4. Bleed
    • 5. Reset the distributor

Before a floor heating system can be put into operation, it must be filled with water just like any other heating system. But underfloor heating has some important points to consider in this work. Each heating circuit must be filled and vented individually. How to vent the underfloor heating, we show you here.

So that the underfloor heating can bring heat into the rooms, it needs water. In the snakes and bows of the long plastic pipes but likes to some air and sometimes mud firmly. Therefore, a floor heating not only has to be completely filled with water at the beginning, but it must also be rinsed from time to time. When flushing, the heating system must be refilled and vented. Therefore, it is not possible with a floor heating, just to open a vent plug, so that the air can escape. If the water is distributed evenly and without air bubbles in the heating pipes, you will be rewarded with an even, pleasant warmth from the ground.

Material and preparation

You need this:

  • Wasserpumpenzange
  • hoses
  • Nozzles
  • water
  • WD 40

Costs and specialist company

Venting underfloor heating is not as easy as venting with a normal radiator. Each heating circuit must be individually vented here. Therefore, it is not sufficient to open the vent plug and to let the air. In the underfloor heating, the air is distributed in several hundred liters of water in the hoses. These pipes or hoses contribute by the entangled laying to the fact that the air is difficult to escape. The air would just move on to another place in the cycle. The costs are very manageable, since you only need two hoses and the corresponding valves. In addition, the hoses are usually already included in the delivery and installation of the heating system from the manufacturer.

  • short hose ends 2 pieces - about 10, 00 Euro
  • Dispensing valves for connection to supply and return - about 8.00 Euro / piece

If you have major problems with air in the pipes, it makes sense to hire a specialist for maintenance and ventilation. This is what most fitters do for between 50 and 100 euros . But ask in advance what the heating engineer estimates to vent the underfloor heating. He will usually ask you which hose or pipe length has been laid and how many heating circuits there are to estimate his approximate cost of labor.

Tip: Be sure to watch the professional at work. The venting can be learned quite well and you will save in future such costs. In addition, you can then often eliminate small problems immediately and do not freeze. If the technician allows it, you can also film the work with your mobile phone.

Shell construction and ventilation

If your building is still under construction, you must not vent or flush the underfloor heating if frost threatens. Otherwise, the water may freeze until you have vented. In freezing weather you should only vent or rinse, if you have sufficiently distributed other heating methods in the building.

Tip: If the system is not working properly, you should rather empty the heating system when it is freezing. But this is only possible with a compressed air compressor, as the underfloor heating does not empty by itself like a conventional heating system. Keep these problems in mind before filling the heater at all.

Instructions - Vent underfloor heating

When you should vent a floor heating, you notice relatively easily by itself. Either individual points on the floor are no longer warm or the entire heating power is insufficient. You will not hear the otherwise common gargling in the radiator with a floor heating. If you are still cold despite the optimum flow temperature, there will certainly be air in your pipe system somewhere. Of course, the manufacturers are not always completely in agreement with the heating systems either. Thus, there may be special features in your heating circuit that deviate slightly from the normal procedure. Therefore, in addition to our instructions, you should also take a look at the manufacturer's operating instructions.

1. Close the flow and return

The cocks for the flow and return are closed in the first step. Subsequently, the heating circuits of the return manifold should be closed. Here is usually a simple handwheel installed, which may be difficult to turn. This often happens when the handwheel has not been used for a long time. Turn carefully but not forcefully.

Tip: If the handwheel is very tight, you can first spray a little WD 40 with the thin red grommet on the moving parts. After a short wait, the bike will certainly spin very easily.

2. Connect main distributor

At the flow distributor is a cock, this often has an open flap, which must first be removed. Here then a corresponding water hose is connected. Most of the heating system has a hose with it from the beginning, which has the right dispensing valves.

3. Connect the return manifold

The second hose is now connected to the tap of the return manifold. Place the end of the hose in a drain or special drain funnel, which is often installed nearby for new systems.


Tip: Pay attention to the system pressure during filling and rinsing. More than 2.5 bar should not build there. For most systems, a safety valve opens at 2.5 bar, which automatically drains off the heating water.

4. Bleed

Now the first heating circuit on the return manifold is opened. Leave it open until only water comes out of the hose. If the complete air has escaped, you can close this heating circuit and vent the next heating circuit in the same way. However, you must never open several heating circuits at once, the heating circuits must always be vented one after the other.

Tip: Basically, venting the floor heating is the same as flushing. So, if you suspect that there are already residues or sludge in the pipes, you should run the water a little longer so that any sludge is immediately rinsed out.

5. Reset the distributor

The distributor is returned to its normal state and the hoses can now be wound up and hung up for the next use in the boiler room.

Tip: Hang the hoses on wide hose holders so that no kinks occur. The hoses are usually used only once a year and hang the rest of the time only on the wall. If the hoses are then hung poorly, they will suffer relatively quickly in the warm room.

Tips for quick readers:

  • if there is a risk of frost, do not vent or rinse
  • Close the flow and return
  • Connect the hose to the main distributor
  • Keep track of system pressure
  • Do not exceed 2.5 bar
  • Connect hose to return manifold
  • Lead the hose end into the drain
  • open first heating circuit on return manifold
  • Bleed until no more air comes
  • close the first heating circuit
  • vent further heating circuits in the same way
  • Put the distributor back to normal condition
  • Remove hoses and hang up
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