Adding cold water during cooking of beans and cooking time
If you want to speed up the cooking time and need to add more water, heat it on stovetop or in microwave till steaming, then add.  Cook at lower heat just at or below simmer to keep beans more intact and with a cover on to avoid water loss in the first place. NEVER add salt at the beginning of the cooking process, only once desired doneness has been reached.  If they just won't get soft (really hard water), add a tablespoon of baking soda to the cooking water, but then they will get soft really fast so watch carefully.