A sampling device uses two ball valves that may be operated to take a sample while allowing flow to continue in a bypass path in a pressurized pipe. As one ball valve closes, it may capture a sample of liquid and gas that may be traveling in the pipe, then the sample may be discharged through a sampling outlet. The second ball valve may be operated simultaneously to open a bypass path while the first ball valve captures a sample. In some cases, the speed of actuation may be a function of the flow speed to capture an accurate sample. In other cases, the length of pipe from the sampling valve to the bypass junction may determine the effectiveness of the sample when actuation speed is relatively slow.