How did the ancients distinguish whether well water was safe without instruments and equipment?

In ancient times, although people were backward in science and technology, they still had their own methods to judge whether well water was safe or not. For example, when digging a well, the ancients did not drink well water for the time being, but put one or two turtles in the well first. If the turtles are alive and well in a few days, it means that the well water is not poisonous, fresh and safe.

Due to the backward technology in ancient times, the material life of ordinary people is far from what it is now. Take drinking water and water for example. Modern people use tap water and can also drink water with a water purifier. In ancient times, it was different. They had to dig a well and carry it home barrel by barrel, even the emperor and the prince were no exception. In the past, there were generally two or three wells in a village, which everyone used together. If well water has safety problems, the whole village will suffer, so at that time, the safety of well water is actually very important.

Well water was safe and often chaotic in ancient times. In order to win the war, the opposing sides often do something out of line, such as sending spies to the other side's territory to poison the well water, so as to deal a blow to the enemy. At this time, the problem of well water safety is highlighted. If there is no good way to ensure the safety of well water, people's drinking water problem can't be solved and personal safety can't be guaranteed.

The custom of raising turtles in wells is magical, but so is the wisdom of ancient working people. Every time they drill a well, they will put several turtles in it. In case the well water is poisonous or poisoned, the tortoise will certainly not live, and will naturally float on the well water with its white belly turned upside down, indicating that the well water is unsafe. This method can be said to be very effective, even if the enemy spy wants to poison, it may not harm people. Later, with the development of history, raising turtles in well water became a folk custom and a way of praying. I hope I can live as healthy and long as a tortoise after drinking well water.