Abstract: Method for maintaining the water balance in a property equipped with a drainage system (4) for waste water, the waste water being conveyed via the drainage system (4) to a waste water container (6). The fresh water that constitutes a part of the waste water is supplied from a fresh water container (7), and the water balance is maintained in the property by supplying a quantity of water to the system, with the fresh water container (7) being replenished from a source outside the property, which quantity is essentially the same as the quantity of water that is led away from the system by the waste water container (6) being drained of waste water and the waste water being transported away from the property.

Abstract: Method for maintaining the water balance in a device (4;5) including a container for waste that has been separated from the waste water, the device (4;5) constituting a part of a permanently installed water purification system for purification of waste water from a building (2). The method is characterised in that the same quantity of water that is removed from the container during sludge suction is replenished to the container before the device (4;5) again is put into full operation.

Abstract: Method for maintaining the water balance in a property equipped with a drainage system (4) for waste water, the waste water being conveyed via the drainage system (4) to a waste water container (6). The fresh water that constitutes a part of the waste water is supplied from a fresh water container (7), and the water balance is maintained in the property by supplying a quantity of water to the system, with the fresh water container (7) being replenished from a source outside the property, which quantity is essentially the same as the quantity of water that is led away from the system by the waste water container (6) being drained of waste water and the waste water being transported away from the property.