We just replaced our vanity in our main bathroom. Now, our tub won't drain. A friend said it was probably because there is air in the line, but I don't know how to remedy this problem. Our house is OLD, and there evidently isn't an air vent in the pipes--again, info from a friend. Meanwhile, I'm washing my hair in the sink and need to get this fixed before the kids go back to school so that we aren't all filthy. (I can only "spit bath" for so long.):eek:

You possibly are getting an airlock. A vent will have to be installed. Try a studor vent under the sink.