1.   Dark stains can sometimes be bleached out with laundry bleach or a solution of oxalic acid and water.

2.   I know I can wash the mildew off with a solution of laundry bleach and water, but what can I do afterwards to prevent this happening again?

3.   If it is due to a buildup of mildew or fungus, then periodically pouring some laundry bleach through that pipe should solve the problem.

4.   The mold can be removed by washing with a solution of one part laundry bleach mixed with four parts water.

5.   There are mildew removing solutions sold in most home centers, or you can use a solution of one part liquid laundry bleach mixed with five parts water.

6.   To remove the mold treat it with a commercial mildewcide or by washing with a solution of one part fresh liquid laundry bleach mixed with three parts water.

7.   We removed the mildew by washing with laundry bleach and also installed an exhaust fan before repainting.

8.   You can also wash off the moss and mildew with a solution of one part fresh liquid laundry bleach mixed with four parts water.