Because even into the early 60s, WH dishwashers only had a mesh cup for a detergent dispenser, they gave no pre rinse to warm up the machine. Even very hot water was cooled when it hit the room temperature load of dishes. The WH Hot Water Booster SLOWLY heated the water above 140F since the tub was uninsulated and the heater was rated at 700 watts. Where the timer paused for heating was called the power soak and it could easily add more than an hour to the 1 wash, two rinse + dry cycle. I have a slightly newer roll out with a detergent dispenser so that it gives the wash, rinse, wash, rinse, rinse, dry sequence and it washed well. I insulated the pull out wash well, the cabinet around it and the lid that locks down on the wash well when it is in operation. None of the impeller machines has a real filter so there can be redepositing of fine particles if you try to load them as tightly as newer dishwashers. The impeller machines can look so neat with the various circular loading patterns. Generally, the machines with metal impellers seem to throw water with greater force than machnes with Bakelite impellers. The leading edge of the Bakelite impeller can vary in smoothness and in sharpness. Nicked impellers do not throw as much water and if they are a little out of balance because of missing plastic, the washing can really suffer because they wobble slightly instead of cutting straight through the water. Xcentric action worked in ABC and Kelvinator machines, but not in a dishwasher.