Been using vinegar with no damage to the washer and good results.
3 things to add:
-Damage doesn't seem likely to me, if anything, it HELPS the washer's longevity by constantly getting rid of hard water sediment. IMO, if anything did happen to the washer, it'd be because of the soap.
-If you put in too much clothing, the vinegar can't rinse properly and you might end up with a relatively strong vinegary smell on your stuff - happened once or twice.
-Making a citric acid solution would fix problem #2, and possible be a more effective water softener/soap scum preventer/remover, but I have no idea how strong of a solution to make. Any ideas lab geeks :mrgreen:?