Powder flow conveying from a powder feeder to a process (i.e. thermal spray gun) can have instabilities that can be detected and diagnosed using a hose back pressure. Incorporating a pressure transducer in a powder hose line at a connection of the powder hose line and the feeder allows the back pressure to be measured in real time at a high sample rate to detect instability and aid in diagnosing a cause of the instability. Diagnosis includes identifying periodic oscillations in the powder hose line such as acoustics as well as detecting hose clogging and hose rupture conditions. Once detected, proper corrective actions can be recommended to correct the cause of the instability.