I heard that the people asked the Prophet of Allah ﷺ: Water is brought for you from the well of Buda'ah. It is a well in which dead dogs, menstrual clothes and excrement of people are thrown. The Messenger of Allah ﷺ replied: Verily water is pure and is not defiled by anything. Abu Dawud said I heard Qutaibah b. Sa'id say: I asked the person in charge of the well of Bud'ah about the depth of the well. He replied: At most the water reaches pubes. Then I asked: Where does it reach when its level goes down ? He replied: Below the private part of the body. Abu Dawud said: I measured the breadth of the well of Buda'ah with my sheet which I stretched over it. I them measured it with the hand. It measured six cubits in breadth. I then asked the man who opened the door of garden for me and admitted me to it: Has the condition of this well changed from what it had originally been in the past ? He replied: No. I saw the color of water in this well had changed.  

سَمِعْتُ رَسُولَ اللَّهِ ﷺ وَهُوَ يُقَالُ لَهُ إِنَّهُ يُسْتَقَى لَكَ مِنْ بِئْرِ بُضَاعَةَ وَهِيَ بِئْرٌ يُلْقَى فِيهَا لُحُومُ الْكِلاَبِ وَالْمَحَايِضُ وَعَذِرُ النَّاسِ قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ الْمَاءَ طَهُورٌ لاَ يُنَجِّسُهُ شَىْءٌ  

"It was said: 'O Messenger of Allah, you perform Wudu' from the well into which the bodies of dogs, menstrual rags and garbage are thrown?' He said: 'Water is pure and it is not made impure by anything.'" (Using translation from Nasāʾī 326)   

أَنَّهُ قِيلَ لِرَسُولِ اللهِ ﷺ يَا رَسُولَ اللهِ أَتَتَوَضَّأُ مِنْ بِئْرِ بُضَاعَةَ وَهِيَ بِئْرٌ يُطْرَحُ فِيهَا الْمَحِيضُ وَلُحُومُ الْكِلَابِ وَالنَّتْنُ؟ فَقَالَ رَسُولُ اللهِ ﷺ إِنَّ الْمَاءَ طَهُورٌ لَا يُنَجِّسُهُ شَيْءٌ