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Dishwasher Drain And Water Supply Installation

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Dishwasher Wiring

Kitchen Sink Drain

Water Shut Off Valve

Most residential dishwashers have the same hook up for the dishwasher drain and the water supply.

The standard dishwasher drain hose size is 5/8"(I.D.) inside diameter on both ends.

The drain, electric, and water connections are all located on the bottom of the dishwasher.

It is Recommended by the manufactures that you install the dishwasher water supply line to the hot water supply.

The water supply line for a dishwasher will have a 3/8" compression connection on both ends.

The dishwasher drain gets connected to either the garbage disposer(if you have one) or gets connected to a "dishwasher tee".

A dishwasher tee gets installed between the tail piece and the trap and creates the connection for the dishwasher drain.

To determine the length needed for the water supply line, drain hose, and the electric wire(for hard wiring direct) you would add three feet to the measurement. Measuring from the shut off valve to the center of the opening in the cabinet for the dishwasher.

The reason you need to add the extra three feet to the measurement is so the dishwasher can be pulled out of the cabinet to be repaired/replaced.

In some areas your local building codes require you to install a dishwasher air-gap between the dishwasher and where it connects to either the garbage disposer or to a dishwasher tee. Air-gaps prevent the back-flow of drain water through the dishwasher drain hose into your drinking water, and the air-gap forms a trap like effect to block the smell from the sewer gases.

Dishwasher air-gaps are recommended to be installed on the sink where the main body of the relief drain for the air-gap is above the sink close to the faucet is the recommended location.

If the plumbing drain line backs up the air gap will divert the water out into the sink blocking the passage to the dishwasher.

Do not install a dishwasher air-gap where the main body is under the sink, if your plumbing system backs up the water would be diverted under the sink and onto floor.

But if your local building codes do not require a air-gap to be installed for the dishwasher drain, you can use the standard method people used before air-gaps... A simple loop in the drain line to block the sewer gases.

Tools Required

The Tools Required To install dishwasher are a crescent wrench, thread tape, channel-lock pliers, wire cutter/stripper, wire nuts, drill, and a 1-1/4"inch wood drill bit.

Double Outlet Shut Off Valve

For the connection under the kitchen sink to the water supply line for the dishwasher, the sink will have a existing single outlet water shut off valve connecting the water supply line to the faucet. But they only have 1 outlet to hook up to.

The easiest way to adapt a single oulet shut off valve for a dishwasher to the hot or cold line is to remove one of the existing shut off valves and install a double outlet shut off valve.

The double shut off valve has two 3/8" compression oulet connections allowing you to hook up two water lines on one shut off valve. You can get a double valve for either a threaded connection to the pipe or for a compression connection to the pipe.

Dishwasher Elbow

You will also need a dishwasher elbow to connect the water supply line to the dishwasher. A dishwasher elbow is simply a brass fitting with 1/2" male threads adapting to a 3/8" compression connection on the other end of the elbow.

Install Dishwasher

Step 1.

Using a 1 wood drill bit, drill the first hole one inch off the back of the cabinet and two inches above the height where the dishwasher drain connects to the sink drain(or garbage disposer). If you are going through more than 1 cabinet to get to the dishwasher, go ahead and drill a hole in the same location through as many cabinets as needed.

Step 2.

Drill another hole(or holes depending on how many cabinets) above or beside your first hole for the water supply.

Step 3.

If the dishwasher tee is already installed or your connecting to the garbage disposal skip to step 6. If you have not installed the dishwasher tee onto the sink drain, place a small bucket or bowl under the trap and remove the trap.

Step 4.

Install the dishwasher tee between the bottom of the kitchen sink tail piece and the trap.

Step 5.

Reinstall the trap.

Step 6.

Wrap thred-tape around the female end of the dishwasher elbow and install the dishwasher elbow into the water inlet valve located on the bottom of the dishwasher.

Step 7.

Install the water supply line to the dishwasher elbow.

Step 8.

Connect the drain hose to the dishwasher using a hose clamp.

Step 9.

Connect the electric to the dishwasher. Wiring For A Dishwasher

Step 10.

Run the water supply line and the drain hose over to under the sink through the holes you drilled.

Step 11.

Being carefull not to pinch the water supply line or the drain hose, slide the dishwasher back into the cabinet.

Step 12.

Connect the drain hose and the water supply to there relative connections under the sink.

Step 13.

Turn on the water and check to see that the dishwasher works and check for water leaks

Step 14.

Mount the dishwasher to the counter top(Refer to your installation instructions).