A pipe abnormality detection system comprising: a pipe comprising a flow inlet , a flow outlet , a first pipe portion , and a second pipe portion , the first pipe portion extending from the flow inlet to a specific position, the second pipe portion extending from the specific position to the flow outlet , the flow inlet allowing inflow of water from a bathtub , the flow outlet allowing the water to pass into the bathtub ; a pump configured to circulate the water between the pipe and the bathtub ; and a pressure detecting sensor configured to detect a pressure of an inside of the pipe , the pressure detecting sensor being placed at the specific position, characterized by further comprising output means configured to output a signal indicating that an abnormality of the first pipe portion is detected, when (i) a difference obtained by subtracting the pressure detected by the pressure detecting sensor during stoppage of the pump from the pressure detected by the pressure detecting sensor during operation of the pump is less than a first threshold (T1) or (ii) a rate of change in the difference with respect to a rotational frequency of the pump is less than a third threshold (T3), and a signal indicating that an abnormality of the second pipe portion is detected, when the at least one of the difference is greater than a second threshold (T2) or the rate of change in the difference is greater than a fourth threshold (T4). a pipe comprising a flow inlet , a flow outlet , a first pipe portion , and a second pipe portion , the first pipe portion extending from the flow inlet to a specific position, the second pipe portion extending from the specific position to the flow outlet , the flow inlet allowing inflow of water from a bathtub , the flow outlet allowing the water to pass into the bathtub ; a pump configured to circulate the water between the pipe and the bathtub ; and a pressure detecting sensor configured to detect a pressure of an inside of the pipe , the pressure detecting sensor being placed at the specific position, characterized by further comprising output means configured to output a signal indicating that an abnormality of the first pipe portion is detected, when (i) a difference obtained by subtracting the pressure detected by the pressure detecting sensor during stoppage of the pump from the pressure detected by the pressure detecting sensor during operation of the pump is less than a first threshold (T1) or (ii) a rate of change in the difference with respect to a rotational frequency of the pump is less than a third threshold (T3), and (i) a difference obtained by subtracting the pressure detected by the pressure detecting sensor during stoppage of the pump from the pressure detected by the pressure detecting sensor during operation of the pump is less than a first threshold (T1) or (ii) a rate of change in the difference with respect to a rotational frequency of the pump is less than a third threshold (T3), and a signal indicating that an abnormality of the second pipe portion is detected, when the at least one of the difference is greater than a second threshold (T2) or the rate of change in the difference is greater than a fourth threshold (T4). <EOS>