Over the last year or so, my Bosch dishwasher (installed in 1999 or so) started to smell skunky, although it still seemed to clean OK if not as well as when new. This slowly worsened, and I started haunting the appliance repair sites.
The main suggestions were to not use so much soap (helped slightly), run a cycle with a cup of vinegar in the water (worked for two days), and (quite oddly) don't rinse the plates off before putting them in the dishwasher. All in all, the washer had worked just fine for years, and none of these are a solution, so kept looking.
Then I happened on an article in an electronics trade rag (Bob Pease's column in "Electronic Design" magazine, 5 May 2011, page 104) pointing out that all the phosphate had just been removed from dishwasher detergents, and this was causing problems. Hmm. Phosphates were always considered essential when I was growing up. What changed?
Using phosphate and dishwasher together as a google search term soon led to the answer, with tale after tale of dishwashers that no longer work, of people buying new dishwashers to no avail ... could this be the reason?
What changed is that the EPA forced the makers of household dishwasher detergents to eliminate all phosphates, despite the fact the phosphate fertilizer is still used by the ton. (Restaurants can still get the phosphate stuff.)
Anyway, the suggested standard solution is to add your own phosphate, and it takes very little to solve the problem - phosphate was about 5% of the mix in the pre-EPA days. In my Bosch, the usual soap load is maybe a tablespoon or a bit more of Cascade, to which I add literally one pinch of Trisodium Phosphate. Swampy smells are gone.
There is however one thing to be careful of: Not everything sold as "TSP" is in fact Trisodium Phosphate these days. I have some "TSP" that was sold to me as Trisodium Phosphate but in fact is Sodium Silicate, which will not work, and may cause damage (the package warns about etching glass). So, read the box carefully. If it does not come out and clearly say that it is Trisodium Phosphate, it probably isn't. It's best to buy Trisodium Phosphate in a real paint store.
For some background, see
Joe Gwinn