CARAV clean water composite exhaust valve is used in the highest point of the pipeline where there is a closed air, to eliminate the gas in the pipe to dredge the pipe head, to achieve normal work, such as not installed exhaust valve, the liquid flowing in the pipe will produce dynamic heat caused by the formation of a short circuit of gas, so that the pipeline outlet capacity can not meet the design requirements, secondly, the pipeline in operation of the power failure, pump stop pipeline will appear negative pressure will cause pipeline vibration or rupture, exhaust (suction) valve will quickly reverse air into the customer, to prevent the pipeline vibration or rupture.