The water supply line to most dishwashers is a rubber tube that runs from underneath the dishwasher and is connected to the dishwashers water pump and the main water supply turn valve usually under the kitchen sink. This main supply valve under the sink usually will have a two way diverted that separates a line that will supply hot water to the sink faucet and the other that will supply hot water to the dishwasher. This line usually runs in conjunctions with, not attached to, the dishwasher waste return line under the sink which in most instances is hooked to the garbage disposal. There is a clamp at either end of both lines to secure the water supply and the waste water line to the water pump of the dishwasher and the hot water main turn valve and the garbage disposal. All you have to do is obtain this supply line. You should probably turn off the water and disconnect the line to ensure you obtain the right length and diameter for the replacement when you go to the store. It is also advisable to obtain new clamps if they are not supplied with the replacement hose. You may want to check that the leak is not coming from somewhere else under the dishwasher and maybe even replace the waste water return line in conjunction with the water supply line. You may want to check that the hose for the supply line is the proper size for you water supply and dishwashers input. The will have adapters if it is larger than your water supply. Your water supply valve could also be bad and the source of the leak if this is new. That is not difficult to replace either and is all in the same job and will not cost more than $10 and most likely half that price.
