Installing a dishwasher can save you a lot of time spent at the sink washing dirty dishes by hand, but it can also be costly to install. If you've decided that you want to do the work yourself, you will need to start by making sure that your existing plumbing under the sink will support it. For example, if you don't already have a dishwasher installed, you'll want to upgrade your two-way stop valve to a three-way valve on your hot water line under the sink. Here's a look at why it matters and how to install it.
Understanding the Purpose of a Three-Way Valve
The standard two-way valve has a single outlet that feeds the faucet of your sink. If you're going to install a dishwasher, you'll need another hot water outlet that will route water to the dishwasher as well. That means changing the valve so that it has an additional outlet. The three-way valve includes an extra outlet that you can use to send hot water to your dishwasher.
Removing the Existing Two-Way Valve
Turn off the water supply to the sink in the kitchen. This will clear the pipes so that you can remove the valve without causing serious water damage. Even with the water turned off at the shut-off valve, you'll still want to put a bucket under the hot water valve before you disconnect it.
Unscrew the compression nuts on the pipe connected to the valve and the faucet. You'll need a faucet wrench for this if you want to make it easy – it's tight quarters to work in otherwise. This will loosen the fitting so that you can remove the riser pipe. Then, cut the supply line with a tubing or wire cutter. Make sure that you cut it as close to the two-way valve as you can. Make sure that the cut is completely square, because you'll need a clean cut so that the new fitting doesn't leak.
Installing the Three-Way Valve
Slide a compression nut onto the cut end of the pipe. Then, add a ferrule. Put the three-way valve on the pipe next, making sure that the ferrule is secure against the threads. The compression nut and ferrule will typically be included in the installation kit with the valve, but you can get them at a plumbing supply shop if you need them. Slide the nut down over the ferrule and tighten it by hand until it's as snug as you can get it.
You'll need to bend and cut new tubing to fit from the outlets of the valve to your sink and to the dishwasher. You may be able to use the existing riser pipe to connect to the faucet, but you'll have to be sure that you closely measure the distance from the valve outlet to the dishwasher input line. Once you have fit your tubing, you can connect the ends of the pipe in the same way, with compression nuts and ferrules. Once everything is connected, turn the water on and watch for leaks at each connection. If there are leaks, add some plumbers tape or something similar.
With these tips, you can install a three-way valve that will add capacity for a dishwasher in your kitchen plumbing. If you aren't comfortable doing the work yourself, a plumbing contractor like Neffsville Plumbing & Heating Services can do the job for you.