A blood treatment apparatus comprising: a blood treatment unit; a blood line configured to extract blood from a blood source, pass the blood through the blood treatment unit and deliver treated blood to a target vessel; and a fluid line configured pass treatment fluid through the blood treatment unit and deliver used treatment fluid to a fluid sink. A flow divider is arranged in the fluid line separates treatment fluid into to a first fluid section and a second fluid section, thereby electrically isolating the fluid sections such that electrical current flowing in the fluid line between the fluid sections is limited. Related manufacturing and verification methods are also described.