Fluid switchover device comprising: a housing comprising at least three ports (11, 12, 13, 14) leading into an interior space of the housing; a valve flap comprising a rotational axis, the valve flap being rotatably arranged within the housing, and the rotational axis being mounted to the housing at a first location and being mounted to the housing at a second location; and a circumferential seal mounted to the valve flap and comprising a first evasion portion at the first location and a second evasion portion at the second location, the first evasion portion and the second evasion portion being configured to evade the rotational axis on the same side of the valve flap, and wherein the valve flap is configured to slidingly engage a boundary of the interior space of the housing by means of the circumferential seal, so that at a first position of the valve flap, the first port is connected to the second port and the first port is sealed off from the third port, and so that in a second position of the valve flap, the first port is connected to the third port and the first port is sealed off from the second port, wherein the circumferential seal projects beyond the valve flap so as to slidingly engage the interior space of the housing, characterized in that the circumferential seal is an O ring held within an O ring holding portion of the valve flap, and the valve flap comprises a first valve flap part and a second valve flap part separated from the first valve flap part, wherein the circumferential seal is continuously in contact with the first valve flap part, wherein the rotational axis is arranged between the first valve flap part and the second valve flap part, and wherein the second valve flap part is not in contact with the circumferential seal at the first evasion portion and the second evasion portion of the circumferential seal. a housing comprising at least three ports (11, 12, 13, 14) leading into an interior space of the housing; a valve flap comprising a rotational axis, the valve flap being rotatably arranged within the housing, and the rotational axis being mounted to the housing at a first location and being mounted to the housing at a second location; and a circumferential seal mounted to the valve flap and comprising a first evasion portion at the first location and a second evasion portion at the second location, the first evasion portion and the second evasion portion being configured to evade the rotational axis on the same side of the valve flap, and wherein the valve flap is configured to slidingly engage a boundary of the interior space of the housing by means of the circumferential seal, so that at a first position of the valve flap, the first port is connected to the second port and the first port is sealed off from the third port, and so that in a second position of the valve flap, the first port is connected to the third port and the first port is sealed off from the second port, wherein the circumferential seal projects beyond the valve flap so as to slidingly engage the interior space of the housing, characterized in that the circumferential seal is an O ring held within an O ring holding portion of the valve flap, and the valve flap comprises a first valve flap part and a second valve flap part separated from the first valve flap part, wherein the circumferential seal is continuously in contact with the first valve flap part, wherein the rotational axis is arranged between the first valve flap part and the second valve flap part, and wherein the second valve flap part is not in contact with the circumferential seal at the first evasion portion and the second evasion portion of the circumferential seal.