A closed conduit system is provided for use in a water supply. The system may include a recirculating unit having a pump and a filter, and first and second pig launch and recovery apparatuses. Each pig launch and recovery apparatus includes a flow tube having a first flow end coupled with the recirculating unit, an opposing second flow end mounted to a hydrant, and a main flow valve. A launch and recovery tube has a first launch end coupled to the flow tube between the first flow end and the main flow valve, and a second launch end fluidly coupled to the flow tube between the main flow valve and the second flow end. An isolated section of the water supply system is defined between the hydrants with the recirculating unit, the pig launch and recovery apparatuses and the isolated section forming a closed circuit.