You may also want to bring your inspector into this, provided you had an inspection. Most inspectors will run the dishwasher while doing the inspection and that should have shown issues with the dishwasher. The other thing that in DC there is an assumed 3yr contract on all work by a contractor. I found this out when I had to sue my builder on a flip over the roof. If all this is starting to add up you may be past small claims court.