1.   A. The stains are caused by water vapor condensing on the cool ducts behind the vents.

2.   First, make sure the metal chimney is stainless steel or aluminum, not galvanized, which could rust and cause the stains on the roof.

3.   First he washed them down with bleach and water, which splattered on the windows, causing indelible stains.

4.   Q. My water has a lot of minerals, and is causing embarrassing stains in my toilet bowl.

5.   Since the stains are caused by moisture, getting rid of the moisture indoors by ventilating and fixing leaks outdoors will go a long way toward a solution.

6.   Sometimes spills cause unsightly stains.

7.   There was enough to cause water stains on the ceilings of the rooms below.

8.   What could be causing these stains?

9.   What causes the stain, and how can it be removed by a homeowner, not a professional cleaning service?