It is quite possible to cook something again in the same water, and nothing will happen to the food.
However, not all products are suitable for re-cooking in the same water. But you can do this to improve the taste of the products and at the same time save on water.
What foods can be re-cooked in the same water
Dumplings or vareniki, eggs or poultry, as well as many other things that do not release fat and dyes when cooked are definitely suitable for cooking.
In the same water, you can cook foods that do not release a lot of their own liquids into the water during the cooking process.
If you cook beets for vinaigrette, then you certainly won’t be able to cook potatoes in this water.
If you take a chicken egg and boil it, and then boil another egg again, you won't have to change the water. But that's if the egg doesn't crack and its contents don't leak into the water.
Water is suitable for re-cooking if the product being cooked in the pan does not release much into the water during cooking.
