I see this problem all the time. if its real bad you have to pull the sump apart and start scrubbing and shopvac it up. then I run citric acid. I tell them to throw away there large packaged old soap or generic soap or whatever and start using "finish" the individually packages ones with the red ball in the middle. Then use dishwasher magic occasionally as needed. I used to buy GE citric acid. Now I buy pure citric acid powder bulk 5lbs on amazon. I keep it in my truck. I have a halfcup measure cup that I use to fill the dispenser and the rest in the bottom. it will shine the stainless right up.