Dishwasher draining problem!

[rej0829]

New to the forum and looking for help and advice! Thanks in advance

When running my dishwasher, it would often and most times leave water behind in the bottom. It would take hours if not a whole day for that few inches of water to go away. I proceeded to examine and found that my drain pipe connected to a small copper pipe that runs through the floor. The copper pipe runs all the way to the main sewer line (about 15 ft of copper pipe). I would assume this was installed because the dishwasher is not directly beside the sink and would require about 12 feet of drain hose to reach the garbage disposal or sink plumbing. I took the drain tube off the of the copper pipe and placed the tube in a 5gal bucket and ran the dishwasher, it drained perfectly. Obviously there isn't a clog from the motor to the drain tube, so its starting somewhere in the copper pipe.

I am not sure if the copper pipe is simply clogged with something from the dishwasher, which could be easily done considering the pipe is less than 1/2 inch all the way to the main line. Could I just gradually cut the pipe down until I find the clog?

or

Is this an air pressure problem not allowing the water to flow properly?

please let me know if you know a solution

 

[Terry]

Normally you would use either an air-gap, or loop the drain high before going down to either a p-trap or a disposer connected to a p-trap.

Are you sure where that copper line is going?

 

[Sponsor]

 

[rej0829]

I don't think I would be able to do that since my dishwasher is so far away from the sink and disposal. My manual states that the drain tube should not exceed 10 ft unless it is going at a downward slope.

 

[Jadnashua]

What is the ID of the copper pipe in relation to the ID of the drain hose? IT looks like the DW's drain line is quite a bit larger than the copper pipe. FWIW, there can be a little water left in the bottom of a DW when it is finished. Another thing to look at is if there is a filter screen and if it is clogged or restricted. The operator's manual should show where it is, and how to fix it if it has one.

Plus, as it is now, if there were a backup in the sewer line, you'd get it going into the DW. And, without installing it either with an air gap or above a p-trap, sewer gasses would be able to freely enter the DW.

If you ran the drain up towards the top of the cabinets next to it, then sloped it down to the drain at the sink, you should be okay if the ID of the line you choose is sufficient. You probably could not push it uphill 10', but it should go to the underside of the counter without issues, then downhill from there.