We've just moved into a rental house that's about 25 years old and know very little about it's maintenance. However, there is a musty odor in rooms near bathrooms and a stronger sour/musty smell in master bathroom. The other room with this musty odor is the laundry. The only room with water that doesn't have any odor is the kitchen. We are replacing the carpet as it is old and musty as well, but I don't think that willl take care of all the odor as it still seems to be with the bathrooms. Any ideas how to start to assess and eliminate possible causes? Thanks.

You are doing all this replacement and considering repair, why isn't the landlord doing this work? It should not be at your expense. Has the home been vacant for any length of time?