Zam Zam is the name of the famous well in al-Masjid al-Haraam [the Sacred Masjid in Makkah, Saudi Arabia]. It provides the water to billions of people, especially during the Hajj for pilgrims. It is the well of Isma’el the son of Ibraheem (Peace be upon them both), from which Allah (Glory be to Him) quenched the thirst of Isma’el when he was an infant. His mother looked for water for him, but could not find any. She climbed to the top of al-Safaa, praying to Allah (Glory be to Him) to help her and give her water for Isma’eel, then she climbed to the top of al-Marwah and did the same. Allah (Glory be to Him) sent angel Jibreel, and he struck the earth with his heels, and water appeared. Linguistically, Zamzam comes from the words zamamtu al-naaqah.  
The well is located only few paces from the Ka’bah, behind the Maqaam (the stepping stone which Ibraaheem used while building the Ka’bah) to the left. Zamzam well is located approximately 20 meters east of the Kaaba or thirty-eight cubits away from the Ka’bah,in Makkah.
Its location is now clearly marked on the marbles of the Mataaf (the nearly circular open space where the pilgrims circumambulate around the Ka’bah). The well itself was lowered below the ground to facilitate the modernization of water extraction from the well, and to remove all obstacles from the path of Tawaaf. Zamzam well is 35 meters deep. 
Zamzam is linked to some of the most important personalities in world history: the Prophets Ibrahim and Ismail (peace be upon them) and Muhammad (May Allah honour Him and grant Him Peace), as well as Ismail's mother Hajir (Hagar) (May Allah be pleased with her).
"This well has never dried up. On the contrary, it has always fulfilled the demand for water. It has always maintained the same salt composition and taste ever since it came into existence. Its portability has always been universally recognized as pilgrims from all over the world visit the Kabah every year for Hajj and Umrah, but have never complained about it. Instead, they have always enjoyed the water that refreshes them. Water tastes different at different places. Zamzam water's appeal has always been universal. This water has never been chemically treated or chlorinated as is the case with water pumped into the cities. Biological growth and vegetation usually take place in most wells. This makes the water unpalatable owing to the growth of algae causing taste and odor problems."
All traditions agree that Allah (Glory be to Him) created the well to provide Hajir, the wife of Prophet Ibrahim (peace be upon him), and her baby Prophet Ismail (peace be upon him) with water in the hot, dry valley they were in, around 4000 years back .
Prophet Ibrahim (Peace be upon him) settled his family there as part of Allah (Glory be to Him)'s command for him. The first thing Hajir (Peace be upon him) had to do then was to look for water in the area. She was searching for it while watching at her son and would run whenever she could not see Ismail. Allah (Glory be to Him) saw her effort and miraculously blessed the spot with a water spring, at the feet of Prophet Ismail (Peace be upon him).
Ismaa’eel’s mother went on breast feeding Ismaa’eel (Peace be upon him)and drinking from the water (she had). When the water in the water-skin had all been used up, she became thirsty and her child also became thirsty. She started looking at him (i.e. Ismaa’eel) tossing in agony. She left him, for she could not endure looking at him, and found that the mountain of al-Safa was the nearest mountain to her on that land. She stood on it and started looking at the valley keenly so that she might see somebody, but she could not see anybody. Then she descended from al-Safa and when she reached the valley, she tucked up her robe and ran in the valley like a person in distress and trouble, till she crossed the valley and reached al-Marwa where she stood and started looking, expecting to see somebody, but she could not see anybody. She repeated that (running between al-Safa and al-Marwa) seven times.
In her desperate search for water, Hajira ran seven times back and forth in the scorching heat between the two hills of Safa and Marwa to provide for her baby who was dying of thirst. Today, this same act is a necessary rite of Hajj pilgrimage all Muslims, mothers and fathers, must complete.
Ibn ‘Abbas (R) said: The Prophet (May Allah honour Him and grant Him Peace) said, “This is the (origin of) the people’s sa’ee (walking) between them between them (i.e. al-Safa and al-Marwa).” When she reached al-Marwa (for the last time) she heard a voice and she said to herself “Shh!” and listened attentively. She heard the voice again and said, “O, (whoever you may be)! You have made me hear your voice; have you got something to help me?” Then she saw an angel at the place of Zamzam, digging the earth with his heel (or his wing), until water appeared. She started to make something like a basin around it, using her hand in this way, and started filling her water-skin with water with her hands, and the water was flowing out after she had scooped some of it.
Ibn ‘Abbas (R) said: The Prophet (May Allah honour Him and grant Him Peace) said, “May Allah (Glory be to Him) have mercy on the mother of Ismaa’eel! Had she let Zamzam (flow without trying to control it) (or had she not scooped from that water) (to fill her water-skin), Zamzam would have been a stream flowing on the surface of the earth.” And he said: “The angel said to her, ‘Do not be afraid of being neglected, for this is the House of Allah (Glory be to Him) which will be built by this boy and his father, and Allah (Glory be to Him) never neglects His people’…”
Ibn al-Jawzi said in his book Mutheer al-‘Azm al-Saakin (2/47): “This hadeeth explains the reason why it is called Zamzam, because when the water flowed, Haajar tried to control it (zammat-ha). The linguist Ibn Faaris said: Zamzam comes from the words zamamtu al-naaqah (I reined in the camel).
With passage of time, the inhabitants of Makkah started to give up the ways of the pious ones. Jurhum, the core of the Makkan population, were driven out of Makkah when they became unjust and tyrannical. They, being fully aware of the importance of Zamzam, hideously plugged it to deny their conquerors its blessings. Zamzam was not reopened and henceforth was forgotten.
Many generations passed in Makkah with Zamzam in complete oblivion, until Abdul-Muttalib (the paternal grandfather of the Prophet Muhammad (May Allah honour Him and grant Him peace)) resurrected the dead well. Abdul-Muttalib himself was oblivious to Zamzam. With the approaching of the last divine message, a sequence of significant preludes was in order; the rebirth of Zamzam was one.
It so happened that for three consecutive nights, Abdul-Muttalib had a very clear vision about digging a well. During each vision, the name of the well was different and no location was mentioned. On the fourth night, however, both Zamzam and its location were communicated to Abdul-Muttalib so clearly that he attended to the appointed task on the morning of the very fourth night.
To the utter disbelief of the Makkans who ridiculed the seemingly futile attempt at finding water in such an arid place, Abdul-Muttalib found water in an ancient buried well so close to the Ka’bah. And it was only natural that the Makkans claim a share in this, obviously, special well. Abdul-Muttalib gave no concessions and rejected any such claim.
After the rebirth of Zamzam on the hands of Abdul-Muttalib, the Makkans accorded Zamzam the veneration it deserved. They used to drink from Zamzam whenever they were about to engage in matter of grave importance.
Al-Haarith Ibn Khaleefah As-Sa’di narrated that Quraysh always commenced their preparation to fend enemies by drinking from Zamzam. This was so customary that one could easily infer the gravity of matters from the collection of pots near Zamzam. The Makkans realized that Zamzam was blessed water. They sought its blessing in matters of gravity, and many a times it was the difference.
The Messenger of Allah (May Allah honour Him and grant Him Peace) said “The best water on the face of the earth is the water of Zamzam; it is a kind of food and a healing from sickness.” Saheeh al-Jaami’, 3302
It was reported from Jaabir Ibn Abdullah (radhi allahu anhu) that the Prophet (sallallahu alaihi wa-sallam) said: “The water of Zam-Zam is for whatever it is drunk for.” Ibn Majah vol: 2, no: 1018 and al-Maqaasid al-Hasanah by al-Sakhaawi, p. 359 Therefore, the scholars recommend that one should make lots of Du'aa while drinking the water of Zam-Zam and he should drink it for a purpose that will benefit him in this world and the next.
The Messenger of Allah (May Allah honour Him and grant Him Peace) said:" The most sublime of all earthly waters is that of zam zam; therein one finds food for the hungry and medicine for the ill." At- Tabarani
It was reported that the Prophet (May Allah honour Him and grant Him Peace) said to Abu Dharr (R): “How long have you been here?” Abu Dharr said: “I have been here for thirty days and nights.” The Prophet (May Allah honour Him and grant Him Peace) be upon him) said, “Who has been feeding you?” He said, “I have had nothing but Zam Zam water, and I have gotten so fat that I have folds of fat on my stomach. I do not feel any of the tiredness or weakness of hunger and I have not become thin.” The Prophet (peace and blessings of Allah (Glory be to Him) be upon him) said: “Verily, it is blessed, it is food that nourishes.” Sahih Al Muslim, 2473 
He also said that the Messenger of Allah (May Allah honour Him and grant Him Peace) had said: “Zamzam water is what one intends to drink for. When one drinks it to be healed, Allah (Glory be to Him) heals him; when one drinks it be full, Allah (Glory be to Him) makes him full; and when one drinks it to quench his thirst, Allah (Glory be to Him) quenches it.” [Ahmad and Ibn Maajah]
Ibn 'Abbas(R) reported: I served (water from) zam zam to Allah's Messenger (May Allah honour Him and grant Him Peace), and he drank while standing, and he asked for it while he was near the House (i. e. House of Allah (Glory be to Him)-Ka'ba). Sahih Al Bhukari 5026
Narrated Ibn Abbas(R): I gave zam-zam water to Allah's Apostle (May Allah honour Him and grant Him Peace) and he drank it while standing.
Asia (a sub-narrator) said that Ikrima took the oath that on that day the Prophet had not been standing but riding a camel. Sahih Al Bhukari 701
Dr. Ahmad Abdul-Qaadir Al-Muhandiss indicates that the results of chemical analyses show thatZamzam Water is pure water, without color or smell, has a distinct taste, and its hydrogen exponent is 7.5, indicating that it is alkaline to some extent.
A study conducted in American laboratories showed that traces of thirty elements were identified in Zamzam water by means of energizing neutrons. Some of these elements scored less than 0.01.
After matching up the chemical analysis to international specifications, especially to the specifications of the World Health Organization (WHO), results proved the portability of Zamzam water as well as its beneficial effect on the body health. Additionally, sodium is very high in Zamzam water and the international specifications do not put a limit to the measurement of its composition.
Zamzam water has also been treated by ultraviolet rays, and microbes have no place to survive in it, which means that Zamzam water preserves its taste and is not a congenial environment for bacteria.
According to various chemical analyses, dry weather make: Zamzam more saline through evaporation, which is, with Allah (Glory be to Him)’s might, good for the human body.
In conclusion, it becomes clear that we should believe in the Prophet’s miracles and that he as described by Allah (Glory be to Him) (what meant): “Nor does he speak of (his own) desire. It is only Inspiration that is inspired.”[Quran.Surah Najm 53: 3-41]
Prophet Muhammad (May Allah honour Him and grant Him Peace) said: “Zamzam water is a lavish meal and a great healer,” and, “Zamzam water is what one intends to drink it for.”Thus, it is a Sunnah to Drink Zamzam water, wash with it, and splash it on a sick person.
In 1908 and 1973, chemical analyses were performed and proved that Zam zam water is indeed free of germs or pollutants. It is considered a mineral water, as its mineral content is 2000 mg/litre. It contained the following minerals: Calcium, Sodium, Magnesium, among many others. Zam Zam is the richest mineral water with Calcium (200 mg/litre). The Prophet Muhammad (May Allah honour him and grant him Peace) was truthful when he said: “Zam Zam is the feed of Hunger”.
Chemical tests proved that Zam Zam water is exceptionally pure and has neither colour nor taste. By international health standards, especially those of the World Health Organization, Zam Zam water is perfectly potable, has good health results and has a high sodium content.
It was also discovered that by the Will of God Almighty, on evaporation, mineral content of Zam Zam increases, however it has no adverse results on health, on the contrary, it is extremely beneficial.
All the above tests proved that Zam zam water is pure and potable as per international standards, and can only confirm the miracles of the Prophet Mohammad (pbuh), whom Allah (Glory be to Him) had said: “NOR DOES HE SPEAK OUT OF CAPRICE. IT IS NOTHING BUT A REVELATION REVEALED (QUR’AN)” Surat An-Nijm (3-4)
ZamZam water level is around 10.6 feet below the surface. It is the miracle of Allah (Glory be to Him) that when ZamZam was pumped continuously for more than 24 hours with a pumping rate of 8,000 liters per second, water level dropped to almost 44 feet below the surface, BUT WHEN THE PUMPING WAS STOPPED, the level immediately elevated again to 13 feet after 11 minutes.
8,000 liters per second means that
8,000 x 60 = 480,000 liters per minute
480,000 liters per minutes means that 480,000 x 60 = 28.8 Million liters per hour
And 28.8 Million liters per hour
means that 28,800,000 x 24 = 691.2 Million liters per day
So they pumped 690 Millions liters of ZamZam in 24 hours, but it was re-supplied in 11 minutes only.
There are 2 miracles here, the first that ZamZam was re-filled immediately, & the second is that Allah (Glory be to Him) Holds the extra-ordinarily powerful Aquifer for not throwing extra ZamZam out of the well, otherwise the world will SINK. It is the translation of the word ZamZam, which means Stop !!!!!!!!!!!! Stop !!!!!!!!!!!!!!! said by Hajir (Peace be upon Her). Zimam is an Arabic word, it is the rope / REIN attached to bridle or noseband & it is used / pulled to stop the running animal.
The Saudi Geological Survey has a “Zamzam Studies and Research Centre” which analyses the technical properties of the well in detail. Water levels were monitored by hydrograph, which in more recent times has changed to a digital monitoring system that tracks the water level, electric conductivity, pH, Eh, and temperature.
All of this information is made continuously available via the Internet. Other wells throughout the valley have also been established, some with digital recorders, to monitor the response of the local aquifer system.
The water level is 3.23 m (10.6 ft) below the surface. A pumping test at 8,000 litres per second (280 cu ft/s) for more than a 24 hour period showed a drop in water level from 3.23 m (10.6 ft) below surface to 12.72 m (41.7 ft) and then to 13.39 m (43.9 ft), after which the water level stopped receding. When pumping stopped, the water level recovered to 3.9 m (13 ft) below surface only 11 minutes later. This data shows that the aquifer feeding the well seems to recharge from rock fractures in neighbouring mountains around Mecca. Zamzam water has no colour or smell, but it has a distinct taste, and its pH is 7.9–8.0, indicating that it is alkaline to some extent and is similar to seawater. Minerals Mass concentration as reported by researchers at King Saud University.
Sodium 133 mg/L (4.8×10−6 lb/cu in)
Calcium 96 mg/L (3.5×10−6 lb/cu in)
Magnesium 38.88 mg/L (1.405×10−6 lb/cu in)
Potassium 43.3 mg/L (1.56×10−6 lb/cu in)
Bicarbonate 195.4 mg/L (7.06×10−6 lb/cu in)
Chloride 163.3 mg/L (5.90×10−6 lb/cu in)
Fluoride 0.72 mg/L (2.6×10−8 lb/cu in)
Nitrate 124.8 mg/L (4.51×10−6 lb/cu in)
Sulfate 124.0 mg/L (4.48×10−6 lb/cu in)
One of the miracles of Zamzam water is its ability to satisfy both thirst and hunger. One of the Companions of the Prophet said that before Islam, the water was called "Shabba'ah" or satisfying. It was filling and helped them nourish their families.
One of the miracles of Zamzam water is its ability to satisfy both thirst and hunger. One of the Companions of the Prophet said that before Islam, the water was called "Shabbaa'ah" or satisfying. It was filling and helped them nourish their families.
After Islam, this powerful ability to quench thirst and fill stomachs remained. Prophet Muhammad said: "The best water on the face of the earth is the water of Zamzam; it is a kind of food and a healing from sickness."
According to the Muslim collection of Hadith, Abu Dharr al-Ghifari, a Companion (Sahabi), noted that when he first arrived in Makkah during the early days of Islam, not only did he satisfy his hunger and thirst but he survived only on Zamzam water for a whole month.
More recently, in the last few decades, scientists have collected samples of Zamzam water and they have found certain peculiarities that make the water healthier, like a higher level of calcium.
Apart from its ability to serve as satisfying food and drink, Zamzam water's health benefits are also commended. Prophet Muhammad (peace and blessings be upon him and his family) said it was a healing from sickness. This is why pilgrims to Makkah to this day collect it in bottles to bring for relatives and friends back home who are ill.
Prophet Muhammad (peace and blessings be upon him and his family) used to carry Zamzam water in pitchers and water skins back to Madinah. He used to sprinkle it over the sick and make them drink it.
Wahab Ibn Munabbah, who was from the second generation of Muslims, said 'I swear by Him in whose possession my life is, Allah (Glory be to Him) Ta'ala will relieve the person of all illnesses who drinks Zamzam to his fill and will also grant him good health.'
For example, despite tight US laws forbidding the import of foreign liquids and fruits, there is an exception made for pilgrims returning from Makkah, who bring water of the Zamzam home for loved ones.