Dishwasher drain weirdness

Help I need to replace my current dishwasher so I bought a new(used) one thinking I can remove the existing connections slide the new one in and away we go. But what I found is the drain from the dishwasher disappears under the floor and connects to some 1/2" copper pipe then to a larger pipe which meets up with the main waste line. Should I just try it and see if it works or try and install it like the manual suggests. Connected under the sink before the trap. Never had any issue with smells or drainage from old dishwasher. It just leaked from the door. Any help or advice would be great.
Thanks

A dishwasher can not legally be drained the way you describe. There are two methods of draining a DW. All drains must have a trap. A DW drain must also be designed with a way to prevent a sewage backup into it. These are accomplished in one of two ways. The way that is always legal is via an air gap device that is on the counter above the DW. From the air gap, the hose goes to the sink drain and connects via a tail piece that is above the sink's P trap. The other way will usually work OK, but is not always going to satisfy local codes, is the high loop method. The drain hose is looped under the counter top then to the sink drain as previously described. You absolutely can not just run the drain hose into the basement and then into a sewer drain. Local (and Canadian) codes may vary somewhat, but not so much as to allow what you have.

Thank you for your reply pretty much as I figured. I have a lot of strange and wrong things going on in this house. So assume I go with high loop method and connect to the waste line above my trap. How low can the trap go relative to the exiting waste line. I only have a small amount of pipe between my sink drain and trap. Maybe a picture will help sorry it's grainy the tape reads about 23".

Cannot see how long your sink tailpieces are, but to install the DW tailpiece below the tee you are either going to shorten the tailpieces to bring the arms up several inches. You need a sink tailpiece to see where it might fit in current layout.

If you cannot do that you will need to lower the sanitary tee in the wall.

As mentioned in a previous post, your plumbing code may (and probably does) require an air gap fitting. If this is the case, you cannot use the high loop installation.

You'd have to replace one of the arms from the sink with one that has a spigot inlet for the DW drain hose. You also may want to check and change if necessary, the T that connects the two arms with one that has a baffle in it. The outlet of the DW is pumped, and without the baffle, it might just shoot over to the other sink and back up. The baffle prevents that.

it can fit anywhere before the P trap. Keywords to see images of pipe are
"tubular continuous waste" because you have two sink drainholes. You can also make your own "tubular continuous waste" assembly even more complex than what you will see, to add in a Wye that receives the dishwasher drain.

After the " tubular continuous waste" stuff comes the regular drain pipes. They are "DWV" pipes. You can put the dishwasher drain Wye in those pipes too; you are not required to use the "tubular continuous waste" pipes as the connection point. Anything before the P trap is OK. Also, you can have the P trap moved too. Keep it the same height and move it sideways or add a bend to move it somewhere else on the same horizontal plane. My saying this is information, good to know, to know your options; it's not a recommendation to do something specific. Also good to know: the dishwasher drain Wye could be called a Tee or a connection. Also good to know: this Wye / Tee / connector can be installed horizontally if rotated upwards, or 45 degrees up, so the dishwasher drain hose drains into it from above.


I typed "tubular continuous waste dishwasher" into my favorite search engine and I got to see an "ADJUSTABLE CONTINUOUS WASTE (w/dishwasher outlet)"

A repair plumber might be good to call in.