Dirt separators restrain impurities contained in the water of closed systems through a decantation process (precipitation of the particles by gravity). An air vent can be connected to the upper connection, while a drain valve, with or without magnetic insert, can be connected to the lower connection. They are used in heating and air-conditioning systems, in central heating systems with boilers, solid fuel generators, heat pumps. In this way the system is protected, in particular the devices such as heat exchangers and high efficiency pumps. They are complete with insulation.