Dishwasher Installation: How to Hook Up a Dishwasher
Today we’ll be going through the process of uninstalling your old dishwasher and reinstalling your shiny new one. Let’s just take a moment to consider the different dishwasher brands and models as well as plumbing, electrical, and drain connections possible in homes of different ages.
Obviously there are many differences that exist. I have installed thousands of dishwashers and can tell you many nightmare scenario stories, but for the most part dishwasher installations are fairly simple with a little help and know-how. Knowing how to remove and reinstall a dishwasher is obviously important for replacement, but it is also helpful for many simple dishwasher repairs such as cleaning debris out of a drain pump or replacing hoses or a motor.
In this article we will examine the three main connections required for dishwasher removal and installation (the water supply, electrical supply, and water discharge), and also new dishwasher pre-installation preparation and leveling. I will also examine direct drain connections as well as through the garbage disposal. Well, enough of the chatter, let’s get to it.
Before beginning the removal of an old dishwasher, the first thing to be done is verify that the proper cabinet dimensions are available. This step is often overlooked because home owners assume that if a dishwasher is present then a new one will fit. However, in some cases the installation of new flooring or countertops around an existing dishwasher can reduce the height of a dishwasher opening and lock the old dishwasher in to place. This is not a pretty picture.
You can sometimes cut the lower frame of the old dishwasher allowing it to be removed, but the new dishwasher must fit in to the existing space, or either the new flooring or the new countertop must be removed. This scenario can also make dishwasher repair difficult or impossible.
Removing the lower panel will allow you to clearly see if the dishwasher’s feet are behind of or on top of the flooring and how much extra room you have to work with.
The most common difficulty with dishwasher removal or installation is old plumbing. Old corroded water valves should be treated with extreme caution. Better yet, they should be replaced. Maybe I’ll do an article on that in the future. But even a light bump can cause an old valve to start leaking.
You should also know where your home’s main water valve is before you start. Sometimes using the homes main water valve is less risky than using the water valve under the sink.
Okay, so the water is off and you have some towels within reach and something like cardboard to protect the floor from damage. You will also need to disconnect the dishwasher from its power source. Sometimes dishwashers are plugged into a receptacle, but 90% of the time they’re direct wired so the home’s breaker panel is a good place to do this. Now I can disconnect the drain line.
The discharge line is either connected directly to the drain with one of the drain fittings, through an air break or air gap, or it is attached directly to the garbage disposal. It’s a good idea to plug that drain hose with something to keep that unwanted water from running out.
If you are connecting directly to the sink drain or garbage disposal you will need to secure the dishwasher’s drain hose higher than the main connection to avoid dirty sink water from back-flowing into your dishwasher. This is called a high loop. An air break can also be used to prevent this from happening.
An air break also acts as a safety device allowing draining water a second way of discharge if there happens to be a clog protecting the dishwasher’s drain pump from unnecessary stress. Water should not normally flow out of the air gap. This would mean that the secondary hose is clogged and should be cleaned, the air gap itself has become clogged, or the garbage disposal is blocked by either food or the pre-installed disposal plug.
Yes, disposals have a knockout plug that needs to be removed before dishwasher installation. You would not believe how often they are overlooked.
From under the dishwasher we can disconnect the electrical and water supply lines as well as raise the legs as much as possible to give us a little more room to lift the dishwasher out, clearing the flooring. It’s a good idea to double check the power leads with a volt meter or sensor before you assume that they’re off. Water plus electricity can equal a very bad day.
I like to cap off the hot lead just for peace of mind. Any lines running through cabinetry, especially a corner cabinet, can be very difficult to replace. One method is to tie a string to the old lines that you plan to remove and then use the string to pull the new lines through the same path, but once the old lines are out that option is gone. I definitely recommend replacing old water lines while you have easy access to the plumbing.
Hard copper is one of the most reliable connections that you can use, but unless you are extremely comfortable working with these types of connections you may be in for trouble. Any cuts must be clean and perfectly round for a new nut and compression ring. Also, the pipe must be at a perfect 90 degree angle to the elbow to avoid cross threading.
You must be able to finger tighten the nut several threads or you will cross thread it.
The dishwasher should be anchored to the top of the cabinet with a few screws. There may also be a few screws passing through the sides of the dishwasher, but this is rare.
Once any mounting screws have been removed tip the dishwasher forward and lift it out. Now you’re clear to replace the lines, clean up, make repairs, do a little half-time dance, whatever you need to do. You may also have to expand the plumbing holes for any larger lines. Once you’re done with the dancing, now would be a good time to prep the dishwasher, which is what I’ll be covering in my next installment of this “How to Install a Dishwasher” series. Keep your eye out for it soon!
Lay the new dishwasher down on its back and remove the lower panel. You can also remove the electrical box cover and install the power cord or power line if you have enough slack. Appliance manufacturers use two main types of water main elbows, male and female. The male type is the most common and requires that you wrap the threads of the elbow with Teflon tape in the clockwise direction three to four times to prevent leaks.
The female style has recently been adopted by Whirlpool and used a very familiar hose connection. However, use caution. If you cross thread this plastic valve you will need to replace the dishwasher’s water valve. If you are using a new water line you can connect it now while everything is easily accessible. If you are reusing an old water line, do your best to get this elbow lined up at the proper angle to meet up with your water connection as you reinstall the dishwasher.
Some dishwashers require that you attach a new drain hose and now would be a good time to do that as well. Drain hoses usually have a universal connection on the end that can be cut for the proper situation. Check twice and cut once. There’s no going back.
It is also nice to loosen up the leveling feet while the dishwasher is on its back making leveling considerably easier when the dishwasher is in place. Most Whirlpool dishwashers have wheels on the back which is strange, but nice. You can roughly set the height of these wheels with the dishwasher out, but any fine adjustment will need to be done in place with wood shims.
At this point you can feed your new connections through the cabinet and carefully move the dishwasher back into place. It’s a good idea to stop half way and make sure everything is going where you want, pull out the slack, check for anything that may be getting caught. In most cases you will now need to make your electrical connections.
It’s a very good practice to install a strain reducer around the conduit. Many building codes actually require it. This will protect the wire from being cut by the sharp electrical box and will also contain any heat that would be generated by a short or a poor wire net connection. Pretty simple, white to white, black to black, ground to the box. Strip any bad wire off for a bad connection and then hold the exposed wires parallel and let the wire nuts twist them together. You do not need to pre-twist the wires.
So while I’m reconnecting this, we’re going to talk a little bit about the hazards of working a dishwasher. A couple things you need to be aware of.
One, be very, very cautions with floors obviously, with scratches when bringing the thing out. And also leaks, especially. When you’re reinstalling the dishwasher it’s very, very important that the dishwasher be level, especially from front to back. Get it straight, or even with the cabinets, or just tipped back slightly. There is no bottom seal at the bottom of a dishwasher in most cases. If there is it’s a light one, it’s not water proof.
If the dishwasher is tipped forward what can happen is those waves that are created just from circulation of the water can cause the water to run up out of the front as the water surges in the tank.
One other thing that’s pretty important, you also need to be absolutely positive that all of your connections are 100% dry. Even small leaks, over time, can cause major damage to flooring and cabinetry.
So after you have got everything working properly you want to sit there for an extended period of time looking underneath the dishwasher to make sure you don’t have any drips or leaks. Leave that lower panel off maybe for a day or two. You never know. Then when the thing’s running take a look and double check.
My grandpa told me this good little trick. You want to use a red napkin, or a colored napkin, and place it down there. If you did see any leaks you need to repair it’ll make a mark on that napkin and you’ll be able to see for an extended period of time, even if you don’t happen to catch it at the moment of the drop. So that’s about it. I hope you found this information and guidance helpful and that you have a well running dishwasher for years to come without the need for any appliance repairs.