What is one way to make stored water safe?

Even though you asked for ONE WAY, I found some other good ways.

1. Thoroughly wash plastic soda bottles or milk jugs with warm, soapy water.

2. Store sealed containers in a dark, dry, and cool place.

3. If after six months you have not used the stored water, empty it from the containers and repeat steps 1 through 3 above.

answerlinnaeus;