Place the water, celery, zucchini, and string beans in a pot and bring to a boil. Lower the heat and simmer, partially covered, until the vegetables are green and tender (not mushy), about 15-20 minutes. Alternatively, you can steam the vegetables if preferred.

Add the fresh parsley and puree the soup using an immersion blender (or transfer to a heat resistant blender like a Vitamix in batches).

Eat warm and enjoy all the healthful benefits!