Home generalRefill water in the heater yourself - 9-step manual

Refill water in the heater yourself - 9-step manual

  • The basic principle
    • Which pressure is optimal?> Refilling the heating water
    • More information
      • How often do you have to refill?
      • Requirements for the hose
      • Always a hose connected
      • Desired heating power is off
      • Strongly lime drinking water
      • Pressure too high

    Winter is coming up and you want to prepare the heating optimally for the cold season? Or you notice in the summer a decreasing achievement of the hot water treatment? Then it's time to check the water pressure and refill the heating water if necessary. This work is carried out quickly in a few steps and restores the complete function of the heating system. Read how often you need to refill and what steps are needed.

    Without a sufficient amount of heating water, the system can not work optimally and functional failures occur. Therefore, it is crucial that you regularly control the pressure. Whether as a landlord, tenant or owner of a family home, the refilling of the heating water can be done in a few steps without the addition of a Heizungsbauers. Just before the onset of winter, it is important to ensure the function of the gas boiler, as in the cold season, the system must work very hard. In our guide you will find out how to fill up the system, then vent it properly and what special features can occur.

    The basic principle

    The refilling of the water depends on the respective system. The basic principle is always the same: you have to fill a certain amount of drinking water into the heating system. For the filling are appropriate taps, the so-called KFE taps, pre-installed. KFE is the abbreviation for Kessel-Füll-Entleer-Hahn. You will usually find the taps at the lowest point of the complete pipe system. Now a suitable water hose must be connected to the tap, or it is already present. In the latter case, it is important that a permanent separation of both water systems is guaranteed, since otherwise heating system water can get into the drinking water.

    Which pressure is optimal ">

    Tip: To avoid accidentally exceeding the upper limit for the water pressure, fill the water slowly and, if necessary, in several increments. If no standard range is marked on the manometer, you will find additional information on optimum pressure in the operating instructions.

    Refilling the heating water

    Make sure that there is a tap near the heating or the KFE tap. The hose must be of sufficient length so that the water can be channeled into the system.

    Step 1: Turn off the circulation pump first.

    Step 2: Completely open the thermostatic valves.

    thermostatic valve

    Step 3: Then take the water hose and connect it to the KFE tap. It is important that you do not tighten the hose yet, as it still contains air that has to escape.

    Step 4: Now take the other side of the hose and connect it to a faucet. Place a system separator between the tap and the hose.


    Step 5: Now you have to open the faucet so that the hose fills completely with water. The air escapes from the hose, but this water can escape from the transition. Place the bucket under the connection and catch the water.

    Step 6: As soon as the hose is completely filled with water, turn it firmly to the KFE cock.

    Step 7: There is a valve on the filling tap, which you now open. The water now runs in the heating system.

    Filling faucet heating system

    Tip: When filling, pay close attention to the pressure gauge so that you can produce the optimum print. Maybe a second person can be helpful here.

    Step 8: Once the right pressure is achieved, close the valve again.

    Step 9: Let the water in the hose run into the bucket.

    More information

    How often do you have to refill ">

    Requirements for the hose

    The operating instructions tell you which hose is suitable for your heating system. Often, a conventional garden hose is sufficient. It is important that you use the hose used only for heating ventilation and then not use again for garden irrigation. The heating water already in the system is not clean drinking water, so that unhealthy deposits can form. Therefore, rinse the hose thoroughly after use and lay it aside for the next time you fill the system. The darker the heating system water is, the more corrosion has taken place inside the system.

    Disconnect heating water and drinking water

    Important: Before connecting the hose, place a system separator on the opening. This special hose connection prevents contaminated heating water from accidentally entering the drinking water system. As a rule, the system separator is placed between the tap and the hose so that the drinking water is optimally protected.

    Always a hose connected

    It is not always necessary to connect a water hose. Some systems already have a connection through a hose, although for safety reasons a separation system is integrated. Since the drinking water system and the heating water system must not be permanently connected to each other, the hose may already be connected, but the interruption is realized by means of a lever and internal shielding.

    In this case, proceed as follows:

    The hose connects the water circulation of the heating with the drinking water system. There is a lever for the separation on the part of the heating system. There is a tap on the side of the drinking water system.

    • First open the lever.
    • Now open the faucet so that the drinking water can flow into the spa.
    • Allow heating water to run in until the correct pressure has been set.
    • Close the tap again.
    • Then close the lever.

    Tip: Pay attention to the exact sequence when opening and closing the lever and the tap, so that the lever does not become too heavy.

    Desired heating power is off

    In this case, it is possible that too much air has entered the system. This process is normal and can be remedied by venting the radiators. Through this flows the heated heating water, so that existing air leads to a reduced performance. To deflate, you need a special heating key, which is available at a very small amount in the hardware store.

    Tip: In order to ensure that the heating output is always optimal, you should vent the heating elements after each filling of the system.

    Bleed the heater

    Also take a look at our article: "Ventilating radiators properly" .

    The escaping liquid is not fresh drinking water but may be heating water mixed with metals. By remaining in the heating pipes heavy metals can settle especially in older systems, so this water should be disposed of without direct contact.

    Strongly lime drinking water

    The calcium in drinking water varies from region to region and can lead to deposits in the system. Depending on how often the system has to be refilled, the risk is greater or lesser. The problem with lime deposits is that they can lead to large defects in the boiler and thus in the worst case, a repair result. Therefore, it is recommended to decalcify hard drinking water before use. For this purpose, mobile decalcification systems are offered that work quickly and effectively. Already affected heating systems can also be decalcified so that the impact of the damage can be minimized.

    Tip: Alternatively, in the specialized trade also preparations are offered, which should prevent the deposition of lime. Prior to use, however, consultation with the manufacturer of the heating system must be consulted, because not in every case a use is safe for the system.

    Pressure too high

    Since too high a pressure is harmful and dangerous, you should avoid filling in too much heating system water. However, modern systems have a safety valve, which opens at too high pressure. For an average single-family home, this safety mechanism comes into effect at around 2 bars, draining excess fluid. As soon as the correct pressure is restored, the water drain stops and the valve closes. However, there is always the danger that this mechanism will not start and the pressure is permanently too high. If it is only a small excess of the standard range, then you can drain the over-filled heating system water by the corresponding tap at the spa:

    • Attach the hose to the thread of the tap (possibly a protective cap is present, which must be removed before)
    • Hang hose in a sink
    • Open the tap so that the water can drain off
    • Close the cock again

    Tip: So that the often rigid hose remains in the washbasin and the heating water does not reach the floor or is splashed in the room, a second person should hold the hose.

    Tips for quick readers:

    • Check water pressure at the spa
    • Use faucet near the gas boiler
    • Place bucket
    • Connect the hose
    • Do not tighten the hose yet
    • Leave air in the hose
    • Connect the hose to the tap
    • Open the valve on the heating system
    • fill until optimal pressure is reached
    • Close the tap again
    • Close the valve and remove the hose
    • Bleed the radiator regularly
    • check pressure every three to four months
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