The bottom is stainless steel, but remember it has a manual food filter, which is plastic. It's the same system I had in my 2004 Siemens dishwasher. No issues. I have the 800 series. On the lower series, "may" have more plastic in the bottom but I think the company would use the same system to cut down on costs. I am replacing my Siemens (Bosch) only because I am remodeling my kitchen and using stainles steel appliances.