Autoclave for sterilisation (1) comprising a sterilisation chamber (2), a tank (3) of water, connection means (4) suitable to connect the tank (3) to the sterilisation chamber (2) in a fluidic through connection, heating means (2a) suitable to heat and to pressurise the water and to supply the sterilisation chamber (2) to perform sterilisation cycles, in which the tank (3) includes a filter (30), the tank (3) is in addition divided into a high potential portion (3a) and a low potential portion (3b), said portions being in reciprocal fluidic through connection through the filter (30), the filter (30) comprising a plurality of filtering layers (31) including distribution layers (34) suitable to slow down and improve the distribution of the water along the entire area of the layers (31) and active layers (33) suitable to perform purification functions of the water.