During a water draw test, horizontal type bidirectional sphere provers with a straight calibrated section of pipe between the detector switches sometimes suffer from sphere launch failure which typically results in a failed water draw test. These types of provers, especially in larger pipe diameters will benefit from an elongate concentric fabricated reducer attached to the outlet of each launch tube. These elongate concentric fabricated reducers result in a successful sphere launch on the first attempt. Assuming all the other components of the prover are properly designed and assembled, a successful sphere launch will result in a successful water draw test on the first attempt saving time, money and reputation.