I'm not sure how far back it should go under the counter. Do I line up the top edge of the dishwasher with the edge of the counter? Do I line up. Those fins are there for you to secure the DW to the underside of the counter top. Installing a Bosch dishwasher depends on what type of countertop you have over. The line of holes on the bracket should point away from the dishwasher.
An improperly installed drain hose is by far the most common defect that I find with dishwasher installations, but it's also one of the easiest things to get right. In the photo below, which was featured as a Structure Tech Photo of the Day, there are several plumbing defects, two of which are related to the dishwasher drain. Can you spot them?
Wrong side of trap
Problem number one is that the drain is connected to the sewer side of the trap. The water that always sits in the bottom of the P-trap is what prevents sewer gases from coming in to the house. The dishwasher drain must be connected before the P-trap, not after it, which is what was done here. With this improper installation, sewer gases have the potential to come back in to the dishwasher. The diagram below right shows a proper installation.
No high loop
In the diagram above, right, you'll notice that the dishwasher drain makes a high loop underneath the kitchen sink. This is the minimum requirement on every dishwasher drain installation - it's required by every manufacturer of dishwasher, and it's also required by the Minnesota State Plumbing Code (section 4715.1250). In fact, our plumbing code says 'as high as possible under the countertop.' An alternative to installing a high loop is to install an air gap at the kitchen sink - it's a device that actually mounts above the sink. I can't imagine why anyone would do this if they didn't have to - how ugly. In some parts of the country, these air gaps are required no matter what. Too bad for them.
Although new dishwashers come from the manufacturer with the drain looped up at the side of the dishwasher, every installation manual still requires this high loop underneath the sink.
I've heard different reasons for why an additional loop is required under the sink, so I decided to contact the manufacturers directly. I sent out an email to eight dishwasher manufacturers, asking them this question:
'A high loop is required on the dishwasher drain in the installation instructions for all of your dishwashers.What is the purpose of this?Doesn’t the high loop that is incorporated in to the side of the dishwasher achieve the same thing?Any insight or commentary in to this matter would be greatly appreciated.'
Here are the responses I received:
- Kenmore: 'The high loop or air gap must be used to prevent potential backflowcontamination of the dishwasher. Local plumbing codes generally dictate the requirements in your area. Section 807.4 of the Uniform Plumbing Code states: 'No domestic dishwashing machine shall be directly connected to a drainage system or food waste disposer without the use of an approved dishwasher airgap fitting on the discharge side of the dishwashing machine. Listed airgaps shall be installed with the flood level (FL) marking at or above the flood level of the sink or drainboard, whichever is higher, or separately trapped with the airbreak located on the stand pipe.'
- GE: 'If an air gap is not required, the drain hose must have the high loop from the floor to prevent backflow of water into the dishwasher or water siphoning out during operation.'
- Bosch: The high loop in the drain hose of your dishwasher is to keep water from settling in the hose if it were hanging down any lower or horizontally. This keeps the drain hose dried out and keeps any odors from backing up into the dishwasher.
- Viking: In testing our dishwashers, we have found that the additional high loop in the back of the dishwasher is required for proper draining of the water. We have seen when this piece is not applied that over time the consumer will have issues with the water back up and causing issues with proper drainage and water pooling in a particular area.
- Maytag: No response after 29 days. Boo.
- Whirlpool: No response after 29 days. Boo.
- Amana: No response after 29 days. Boo.
To summarize, the reasons for the high loop are to prevent potential backflow of water in to the dishwasher and to prevent improper drainage of water. Even though dishwashers come from the factory with the drain looped up high against the side of the dishwasher, this is not an acceptable substitute for the high loop underneath the kitchen sink. In Minneapolis, the lack of a properly installed high loop under the kitchen sink requires repair for their Truth-In-Sale of Housing evaluations.
Reuben Saltzman, Structure Tech Home Inspections - Email - Minnesota Home Inspections
Related Articles
- 1 Anchor a Dishwasher to the Side of Cabinets
- 2 Install a Dishwasher Under a Quartz Countertop
- 3 Install Dishwasher Clips
- 4 Raise a Dishwasher off the Floor
If you're remodeling, purchasing a new dishwasher or just want your old dishwasher to fit flush, keep one thing in mind: Installing dishwashers is routine. The appliance's optimum orientation may be slightly different than you think it should be, due to vents and door position, but with a little help, you can install that dishwasher to fit flush and forget about it.
Position
A dishwasher's position is important to preserve your cabinets and countertops. Look at some pre-existing installations. The door of the dishwasher is typically not flush with the cabinets, but instead it protrudes out from the face of the cabinets about an inch or more. This is so that the dishwasher doesn't vent steam inside the cabinets when it's in dry mode. In addition, if the dishwasher is too far back inside the cabinets, the front lip of the face frame interferes with the top of the door. Therefore, the correct positioning is to set the front of the dishwasher -- not the door -- flush with the front of the cabinets. The door protrudes just enough so that the contact point between the door and the front of the dishwasher is visible.
Dry Fit and Fillers
Dry-fit your dishwasher before installing it. Push it back into place in the opening, with the front of the dishwasher flush with the sides of the face frame on the cabinet. It's likely that there is a gap on one or both sides between the cabinet face frame and the dishwasher. If the gap is more than about 1 inch, it might be necessary to cut and place some fillers to achieve the built-in flush look. Measure the gap between the dishwasher and cabinets on both sides. Cut matching hardwood fillers to span this gap on each side -- or only one side if the dishwasher looks balanced when pushed to one side. Finish them to match the cabinets and screw them onto the side or sides of the cabinet face frame.
Wiring and Plumbing
There may not be much room behind your dishwasher when it's in position. Evaluate how much room there is by first hooking up the water and electrical lines with the dishwasher pulled away or out of the opening as far as possible. Coil as much of the wires and pipes as possible into a flat circle and place them behind the dishwasher. Push the dishwasher into place. If the wires or pipes begin to kink or buckle, pull the dishwasher out, recoil everything and repeat sliding it in until the wires and pipes fit comfortably behind the dishwasher without bending.
Attach
Open the door on the dishwasher. It will expose two metal straps or clips on both sides at the front on top. The clips are designed to bend upward and flatten out on the underside of the countertop. If they fit, place a 5/8-inch screws in the pilot holes on the end of the clips, and use a screwdriver to drive them into the bottom of the countertop to secure the dishwasher. If the clips are too short, measure the gap between the top of the clip and the bottom of the dishwasher. Cut a small block of wood to the measurement. Glue and screw the block to the underside of the countertop, bend the clip up and screw the clip to the block to finish the flush installation job.
About the Author
Specializing in hardwood furniture, trim carpentry, cabinets, home improvement and architectural millwork, Wade Shaddy has worked in homebuilding since 1972. Shaddy has also worked as a newspaper reporter and writer, and as a contributing writer for Bicycling Magazine. Shaddy began publishing in various magazines in 1992, and published a novel, “Dark Canyon,” in 2008.
Photo Credits
- Jupiterimages/Photos.com/Getty Images
Choose Citation Style
Shaddy, Wade. 'How to Install a Dishwasher Flush With a Cabinet.' Home Guides | SF Gate, http://homeguides.sfgate.com/install-dishwasher-flush-cabinet-79907.html. Accessed 23 June 2019.
Shaddy, Wade. (n.d.). How to Install a Dishwasher Flush With a Cabinet. Home Guides | SF Gate. Retrieved from http://homeguides.sfgate.com/install-dishwasher-flush-cabinet-79907.html
Shaddy, Wade. 'How to Install a Dishwasher Flush With a Cabinet' accessed June 23, 2019. http://homeguides.sfgate.com/install-dishwasher-flush-cabinet-79907.html
Note: Depending on which text editor you're pasting into, you might have to add the italics to the site name.