| I am a plumber and i can tell you firsthand they are trying to feed you a bunch of baloney. Both washing machines and dishwashers have a timed fill cycle. When you turn the washer on the timer allows four or five minutes to fill the tub before it advances to the run stage. That is more than ample fill time, even with low water pressure. The machines also have a water level sensor that measures the water level and turns the fill valve off if the tub is full before the time runs out on the timer. In this manner the machines can be used under nearly all residential water pressure conditions without requiring any adjustments. The discharge line from the machine is the same size and the rate of discharge remains the same because both portables and builtins use the same pump to discharge, therefore it wouldn't matter if it is connected to a uniCouple or connected to the drain system in the normal manner. Both dishwashers and washing machines are required to be connected to the drains by means of an approved "Indirect Waste" method. In the case of a washing machine an approved indirect waste can be achieved by either discharging into a sink or into a washing machine standpipe. Due to changes in the design of washing machine pumps they now require a 2" diameter drain line for a standpipe, but in instances where you do not have an 1-1/2" line you may discharge the washer into a utility sink which can be connected via an 1-1/2" drain line. In order to create the required indirect waste receptor for a builtin dishwasher you may discharge it into the dishwasher inlet port on a garbage disposal or you may install an air gap on the counter top. The dishwasher line is connected to the air gap inlet port, and a second line is connected from the air gap outlet port to a dishwasher inlet port type tailpiece under the sink. (In some jurisdictions ALL dishwashers are required to have the air gap). When using a portable dishwasher the drain line runs to the unicouple which is attached to the faucett. This keeps the ourlet of the drain line 2" above the flood level rim of the sink, which provides the required indirect waste air gap. | 
