Abstract: A main water supply (1) is equipped with a main valve (2) followed by a first main pipe (3) running through a first check valve (4), and further to a first adapter (6) while a pilot pipe (7) runs from the main valve (2) through a secondary valve (9) and further a pilot coupling (16). A pressure pipe (12) runs to a secondary valve (9). From the first main pipe (3), a branch pipe (26) runs through a second check valve (28) to a water heater (27) and a second main pipe (29) runs to a second adapter (6.1) through a third check valve (30). A solenoid valve (17) is operated by a timer (18) or by the control signal of a household appliance. Pressure sensors (23, 33) signal of a household appliance. Pressure sensors (23, 33) signal to lamps (23, 34) on a panel(25).