Pump system, in particular a booster pump system, comprising - at least one pump unit, - at least one valve member (40, 50), having a first thread (41, 51), and - at least one manifold (60, 70) with a manifold tube (61, 71) having at least one manifold connecting pipe (62, 72), wherein - the pump unit comprises a pump casing with at least two hydraulic connection ports (20, 30), at least one of the hydraulic connection ports (20, 30) comprises a connecting pipe (21, 31) which is integrally connected to the pump casing and which has a flange (22, 32), - a union nut (23, 33) is held on the connecting pipe (21, 31) between the flange (22, 32) and the pump casing so that the union nut (23, 33) is held back by the flange (22, 32), the union nut (23, 33) of the pump unit is screwed to the first thread (41, 51), - the manifold connecting pipe (62, 72) is integrally connected to the manifold tube (61, 71) and has a manifold flange (63, 73), wherein a manifold union nut (64, 74) is held on the manifold connecting pipe (62, 72) between the manifold flange (63, 73) and the manifold tube (61, 71) so that the manifold union nut (64, 74) is held back by the flange (63, 73), characterized in that, - the manifold (60, 70) is a discharge manifold with a discharge manifold tube having at least one discharge manifold connecting pipe with a discharge manifold flange and a discharge manifold union nut, - the valve member (40, 50) is a check valve member, and - the pump system further comprises a discharge valve member, - the discharge manifold union nut is screwed to a thread of the discharge valve member, - the union nut (23, 33) is a discharge union nut that is screwed to the first thread of the check valve member, and - the check valve member is directly hydraulically connected to the discharge valve member. - at least one pump unit, - at least one valve member (40, 50), having a first thread (41, 51), and - at least one manifold (60, 70) with a manifold tube (61, 71) having at least one manifold connecting pipe (62, 72), wherein - the pump unit comprises a pump casing with at least two hydraulic connection ports (20, 30), at least one of the hydraulic connection ports (20, 30) comprises a connecting pipe (21, 31) which is integrally connected to the pump casing and which has a flange (22, 32), - a union nut (23, 33) is held on the connecting pipe (21, 31) between the flange (22, 32) and the pump casing so that the union nut (23, 33) is held back by the flange (22, 32), the union nut (23, 33) of the pump unit is screwed to the first thread (41, 51), - the manifold connecting pipe (62, 72) is integrally connected to the manifold tube (61, 71) and has a manifold flange (63, 73), wherein a manifold union nut (64, 74) is held on the manifold connecting pipe (62, 72) between the manifold flange (63, 73) and the manifold tube (61, 71) so that the manifold union nut (64, 74) is held back by the flange (63, 73), - the manifold (60, 70) is a discharge manifold with a discharge manifold tube having at least one discharge manifold connecting pipe with a discharge manifold flange and a discharge manifold union nut, - the valve member (40, 50) is a check valve member, and - the pump system further comprises a discharge valve member, - the discharge manifold union nut is screwed to a thread of the discharge valve member, - the union nut (23, 33) is a discharge union nut that is screwed to the first thread of the check valve member, and - the check valve member is directly hydraulically connected to the discharge valve member.