Feed water from the feed water tank S.001 is pumped by the feed pump P.001 into the MD-Module M at the Condenser inlet (C). In the condenser channel the temperature of the feed water will be increased before it enters the heat exchanger for further temperature increase. Afterwards it enters again the MD-Module at the Evaporator inlet (E IN). Here a part of the water evaporates and the vapor permeates through the membrane. On the opposite side the vapor condenses and liquid distillate is formed in the distillate channel. The distillate and the brine exits the MD-Module. The brine is recirculated to the feed tank while the product water is collected in the distillate tank S.002 and from there redirected to the feed tank S.001,The MD unit can be subdivided into three hydraulic circuits: The desalination circuit; including the MD Module M, a cartridge filter F.001 the feed pump P.001, the feed tank S.001 and the flow indicator FI.001. The refilling circuit; including the refilling pump P.002 and a cartridge filter. The distillate circuit; including the distillate tank S.002, the distillate pump P.003.Desalination circuit: The desalination circuit is controlled by three switches, two of them protect the system and especially the MD Module of too high temperatures: Firstly the stop thermostat Q2 TC010 defines the stop temperature (set value e.g. 80°C) of the desalination circuit. The sensor is placed at evaporator inlet. The feed pump P.001 is only in operation when the temperature at this point (e.g. 75°C) is under the set value. Secondly the Stop thermostat Q3 TC011 is located at the primary side of the heat exchanger to stop the operation of the feed pump if the heat source temperature (e.g. 95°C) rises over the set value (e.g. 85°C). Thirdly the floating switch L3F at the bottom of the feed tank has to be closed, so there is water in this storage and the system doesn’t run empty. If these switches are in the right condition, finally the feed pump can be switched on and controlled manually with the potentiometer Poti at the Control Panel CP.Refilling circuit: The refilling pump P.002 is driven by the water-level in the feed tank S.001 and its floating switches in the middle L2F and at the top L1F of the tank. The refilling pump runs only if the water-level in the tank gets below the L2F and stops when the level reaches L1F. The overflow lance in the feed tank is constructed to allows the hot medium, in the higher layer of the tank to flow out while refilling the system by the pump P.002 Distillate circuit: When the distillate tank S.002 becomes full, the distillate pump P.003 is started by the upper floating switch LF top dest L1D the emptying runs time controlled and pumps out e.g. 10 liters. The button B1 on the CP connected to the Pump P.003 allows drafting tab water out of the pipe B.005 while pushed. If the tank S.002 is empty the floating switch L2D will stop the tab function to protect the pump P.003.