Installing a dishwasher water line is a relatively easy task that requires only a screwdriver and a small adjustable wrench as long as there is already an existing hot water stop valve under the kitchen sink for your use.
A few years ago running a dishwasher line was a far more difficult task where you had to pick up 3/8” copper tubing, and compression fittings, and then carefully straighten it out taking care not to kink the tubing. If the tubing were to kink the entire line would be no good, as it would end up leaking at the kink. Not long ago braided stainless steel supply lines became widely available and they are by far the best way to connect dishwashers available. They are available in varying lengths and some even come with a variety of adapters for making connections to the solenoid valve on the dishwasher. If you have a 3/8” compression connection already installed on the dishwasher you will not need these adapters but in some cases new dishwashers do not have the adapter installed in which case you will need them. If you do need to install an adapter the ones that use pipe thread, which is a connection that doesn’t seal with a rubber washer will require the use of Teflon tape and Teflon paste on the threaded connection to seal it and prevent leaks.
If there is not a an existing stop valve you will need to shut off the water to your home, Cut the hot supply, and install a tee and a stop valve. Depending on the pipe material there are many options some of them requiring virtually no plumbing skills such as SharkBite tees and valves or, Sioux Chief’s Add-A-Line Full Slip Valve Tee.
Selection of the stainless steel braided connector is pretty easy just measure to make sure that you are buying one long enough to reach. If you require a longer length you can join two together by buying a 3/8” compression union and discard the nuts and ferrules. I advise against using the Watts FloodSafe supply lines but the Watts Quick’N Easy are okay. The Watts FloodSafe supply lines have a valve which is supposed to close preventing floods when the stainless braided hoses burst but has proven to be prone to nuisance trips and some have had connection failures.
To install the dishwasher supply line with the kick plate removed from the bottom of the dishwasher simply feed the supply line through a hole in the side of the cabinet in the rear corner under the sink into the space under the dishwasher. I like to take the new line with the curve of the coil from being rolled up, so the line is directed to the front of the dishwasher and push it through this usually gets the line under the dishwasher where you can reach it. Pull the line to the front left corner of the dishwasher where the inlet valve is located and connect it to the 3/8” compression connection and tighten with the adjustable wrench. No Teflon tape or, paste is needed on this connection because there is a rubber seal in the connector that provides all the sealing needed. After connecting the dishwasher end move back under the sink and route the dishwasher line across the back of the sink cabinet and connect the other to the extra stop valve on the hot supply line leading up to the sink faucet. Again tighten this with the adjustable wrench and no Teflon tape or paste is needed. You are now ready to turn on the valve and check the connections at each end for leaks. Once you are sure that neither connection is leaking you can use the screwdriver to install the dishwasher kick plate and the dishwasher is ready for use.