At the very least, if you insist on soaking, don’t throw away the soak water, use it to cook the dal or beans. Wash the beans first, throw away the wash water. When they are clean, soak in fresh water and the use that soak water to cook the beans. Remember, rajmah (kidney beans) and black beans are toxic and require 10 minutes at a full boil to break down the toxins and render them safe.