Replace a Dishwasher: Water, Power, Drain and Leak Test

Roger Wakefield, a plumber with over 38 years of experience and every master endorsement in the state of Texas, replaces the dishwasher in his own home, and he points to a small detail that causes many service calls: the knockout plug in the garbage disposal. If a dishwasher drain hose connects to a disposal and that plug has not been knocked out, the dishwasher won't drain. He says people call him after changing a disposal because the dishwasher stopped draining.

Removing the old dishwasher

He starts by taking off the front panel and the top cover screws to see the connections before shutting anything off. The water supply is shut off at the angle stop under the kitchen sink, and he puts a rag down and loosens the nut with an adjustable wrench to drain the line. He notes Teflon tape on the compression threads and says a properly made connection should not need it.

The power cord plugs in at the back, so once the unit is slid out he unplugs it and does not need to turn off the breaker. He removes two set screws at the top that keep the unit from tilting. He then loosens the stainless steel clamp on the drain hose where it meets the disposal. The new drain hose is fed through the same hole as the old one.

Preparing the new unit

He opens the new dishwasher and checks inside for the instructions and the mounting pieces. The new unit has a different water connection at the back, so he swaps the copper line for a flexible hose with a 90-degree adapter. This lets him make the connection under the sink instead of reaching to the back of the dishwasher. He connects it to the angle stop and turns the water on to check for leaks before sliding the unit in.

For power, he moves the cord from the old dishwasher to the new one at the access panel. Green goes to green because it is the ground. The other two can go to the black or the light-colored wire either way. He clips the cord into the channel under the unit and fits the protective sticker along the countertop underside, which he says probably helps keep the electronics from heating the counter.

Setting and leveling

The legs are screwed all the way in so the unit slides without breaking one off. Mounting clips on top show where the counter edge should sit. He slides it back to the edge of the cabinet, checks the door seal, and puts a level in the drum. Once the position and level are right he drives the mounting screws, since they lock the unit in place.

Drain and testing

He attaches the drain hose to the disposal inlet with the hose clamp and says it must not be in a bind, because the dishwasher has a pump and needs a free-flowing path. He removes all tape, foam, plastic and tags from the tub and runs a full cycle while checking water lines, drain lines and under the unit for leaks. Finally he adjusts the rear foot and front feet so all touch the ground, and installs the kick plate.