Process for the manufacture of a tank having high barrier properties toward fluids, comprising at least the following stages: a) manufacture of one or more components by injection molding a polyamide composition; and b) assembling the component or components obtained in stage a), optionally with one or more other components, in order to obtain the tank; said polyamide composition comprising from 5% to 40% by weight of agent which modifies the impact strength and exhibiting the following characteristics: - a melt viscosity of between 50 and 700 Pa.s, measured according to the standard ISO 11443, at a shear gradient of 1000 s -1 and a temperature equal to the melting point of the polyamide + 35°C; and - a permeability to gasoline SP95 E10 of less than or equal to 10 g.mm/m 2.day, measured at a temperature of 40°C and a relative humidity of 20%, said composition comprising: - at least 20% by weight, with respect to the total weight of agent which modifies the impact strength, of an agent which modifies the impact strength comprising functional groups which react with the polyamide, and/or - at least 10% by weight, with respect to the total weight of agent which modifies the impact strength, of a compatibilizing agent comprising functional groups which react with the polyamide, and said polyamide composition being devoid of cyclodextrin and silica, and comprising a novolac resin. a) manufacture of one or more components by injection molding a polyamide composition; and b) assembling the component or components obtained in stage a), optionally with one or more other components, in order to obtain the tank; said polyamide composition comprising from 5% to 40% by weight of agent which modifies the impact strength and exhibiting the following characteristics: - a melt viscosity of between 50 and 700 Pa.s, measured according to the standard ISO 11443, at a shear gradient of 1000 s -1 and a temperature equal to the melting point of the polyamide + 35°C; and - a permeability to gasoline SP95 E10 of less than or equal to 10 g.mm/m 2.day, measured at a temperature of 40°C and a relative humidity of 20%, said composition comprising: - at least 20% by weight, with respect to the total weight of agent which modifies the impact strength, of an agent which modifies the impact strength comprising functional groups which react with the polyamide, and/or - at least 10% by weight, with respect to the total weight of agent which modifies the impact strength, of a compatibilizing agent comprising functional groups which react with the polyamide, and said polyamide composition being devoid of cyclodextrin and silica, and comprising a novolac resin. - a melt viscosity of between 50 and 700 Pa.s, measured according to the standard ISO 11443, at a shear gradient of 1000 s -1 and a temperature equal to the melting point of the polyamide + 35°C; and - a permeability to gasoline SP95 E10 of less than or equal to 10 g.mm/m 2.day, measured at a temperature of 40°C and a relative humidity of 20%, - at least 20% by weight, with respect to the total weight of agent which modifies the impact strength, of an agent which modifies the impact strength comprising functional groups which react with the polyamide, and/or - at least 10% by weight, with respect to the total weight of agent which modifies the impact strength, of a compatibilizing agent comprising functional groups which react with the polyamide, and