Contractor Duane Johnson recalls accompanying a city crew that was proud of its brand-new combination truck. They were trying without success to clean grout from a line. Johnson suggested switching to a high-speed rotating nozzle.
Upon deploying the nozzle, the operator looked at the pressure gauge, went into a panic, and hit the truck’s kill switch. He said the truck should not be operating at such a high pressure at the engine rpm he was using.
Upon questioning, it turned out that the truck had never developed adequate pressure because the crew had been using for the past eight years a single
