Islamic Fiqh > Purification (Tahara) > Water: categories and rulings > The categories of water: detailed rulings
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Updated on 27 September 2026 at 3:52 AM
The jurists divide all water into 4 categories: mutlaq water, used water, heated water and mixed water. This page sets out each category in detail, with the maximum number of opinions attributed to the schools: definitions, evidence, internal divergences of each madhhab and exact references to the classical compilations from which all of this is drawn.
The principle that governs the chapter: water is, in origin, pure and purifying; only an established impediment removes it from that status. The positions below show where the schools agree, where they diverge, and on what texts.
Water is defined as a subtle, fluid body by which every growing being lives (al-Durr al-Mukhtar, 1/179). The jurists call "mutlaq" the water to which the name of water applies without any necessary qualification: one says "this is water", "I drank water", "Allah created water as a mercy for the worlds". It is either water remaining in its original creation, or water changed by what is inseparable from it, such as water flowing over sulphur in its bed; qualifications like "sea water" or "well water", though real, are not indispensable (al-Furuq, 2/216; al-Sharh al-Kabir of al-Dardir, 1/56; Mughni al-Muhtaj, 1/74).
It is also said: mutlaq water is that which remains upon its original creation (Kifayat al-Akhyar, 53), which no impurity has touched and over which no pure substance has prevailed (al-Tarifat of al-Jurjani, 1/250).
The jurists agree that mutlaq water is pure in itself and purifying for other than itself (al-Ijma of Ibn al-Mundhir, 20; Fath al-Qadir, 1/21; al-Sharh al-Kabir, 1/56; Mawahib al-Jalil, 1/56; al-Majmu, 25/39; Kifayat al-Akhyar, p. 53; al-Iqna of ash-Shirbini, 1/21; Mughni al-Muhtaj, 1/74; al-Mughni ma'a al-Sharh, 1/30; Kashshaf al-Qina, 1/26).
They designate it with the term "tahur", while diverging on its meaning. The majority (jumhur), the Malikis, Shafi'is and Hanbalis, holds that tahur is purifying water. Ibn Hubayra reports: the philologists said: tahur is what performs purification in something else, just as one says "qatul" for what kills; Tha'lab said: tahur is pure in itself and purifying for other than itself; on this point only some companions of Abu Hanifa diverged, saying: tahur is the pure, as an intensifying form (al-Ifsah, 1/35-36; al-Bahr al-Ra'iq, 1/70).
An-Nawawi specifies: tahur, in our view, is the purifying water; this is the view of Ahmad ibn Hanbal; some of our companions narrate it from Malik; and it is narrated from some companions of Abu Hanifa and some philologists that tahur is the pure (al-Majmu, 2/21-22; Nayl al-Awtar, 1/565; al-Tahqiq of Ibn al-Jawzi, 1/19).
The evidence of the majority. The first is Quranic:
"And We sent down from the sky purifying water"
Surah al-Furqan, 48
Al-Qurtubi comments: "purifying water" means water with which one purifies oneself, as one says "the ablution of water", that with which one performs ablution; every tahur is pure, but not every pure thing is tahur; tahur, with the fatha on the ta, is a noun, like "ablution" and "fuel", while with the damma it is the verbal noun: this is the known meaning in philology, said Ibn al-Anbari. He thus establishes that the water sent down from the sky is pure in itself and purifying for other than itself: tahur is an intensifying form applied to the pure, and this intensification requires that it be pure and purifying. It is also said: "tahuran" means "pure", and this is the view of Abu Hanifa, who attaches it to the verse:
"And their Lord will give them a purifying drink"
Surah al-Insan, 21
the term meaning, in his view, "pure". Al-Qurtubi adds: the community agreed, linguistically and legally, that the description "tahur" applies only to water and does not extend to other liquids, though they are pure; their restriction to water is therefore proof that tahur is the purifying water (Tafsir al-Qurtubi, 7/39-40).
The second piece of evidence: the hadith on the sea. The Prophet (peace and blessings of Allah be upon him), asked about sea water, said:
It is the tahur: its water is purifying.
authentic hadith, commented on by an-Nawawi (al-Majmu, 2/22-23; Nayl al-Awtar, 1/55)
An-Nawawi specifies: they asked about the purifying character of sea water, not about its purity; had they not understood in tahur the purifying, the answer would not have addressed their question (al-Majmu, 2/22-23).
The third: the saying of the Prophet:
The earth was made for me a place of prayer and a tahur.
reported by al-Bukhari (335) and Muslim (522)
An-Nawawi says: it means a purifying earth; it is by being purifying, and not by being pure, that this community is distinguished (al-Majmu, 2/22-23). Ibn Hajar writes in Fath al-Bari: "and a tahur": it is argued from this that tahur is the purifying for other than itself; if tahur meant the pure, the distinction would not follow, yet the hadith was reported precisely to establish it. Ibn al-Mundhir and Ibn al-Jarud reported, with a sound chain from Anas, going back to the Prophet: "Every good land was made for me a place of prayer and a tahur"; "good" means "pure": if "tahur" meant "pure", the same meaning would be stated twice, which is impossible; it therefore means the purifying (Fath al-Bari, 1/522).
The evidence of the Hanafis. The first: the verse of al-Insan quoted above: the people of Paradise need no purification from ritual impurity or filth, so tahur there means the pure (al-Bahr al-Ra'iq, 1/70; al-Dhakhira, 1/169; al-Majmu, 2/22; al-Hawi al-Kabir, 1/38).
The second: the verse of Jarir describing women: "the saliva of their lips is tahur": yet saliva is not used for purification; he meant the pure (previous sources).
An-Nawawi answers on behalf of his companions: Allah described that drink with the highest attribute, purification; as for Jarir's verse, it is proof for us: the poet wanted to prefer those women to all others, so he described their saliva as purifying, on account of their perfection and the sweetness of their saliva; the verse in its literal sense would give no distinction, for the saliva of all women is pure, and indeed that of the cow, the sheep and every animal, except the dog and the pig (al-Majmu, 2/25).
Water mixed with something pure divides according to 2 criteria: does the mixture change one of the water's attributes, taste, colour or smell? and can the pure substance be avoided? Each combination receives its own ruling.
First case: water mixed with a pure substance without any change. The jurists of the 4 schools agree: a pure thing that blends with water without changing it, however small, does not prevent purification with it, for the water remains in its original state.
Second case: water that has met a pure substance impossible to avoid, and has changed. The 4 schools agree: purification with it remains valid. Such are algae and moss, everything that grows in water, tree leaves that fall into it or that the wind throws into it, twigs and straw that floods deposit in it, and what lies in the bed of the water, like the sulphur over which it flows while changing, or what is in the ground where the water settles: it is hard to guard against them (al-Hidaya Sharh al-Bidaya, 1/18; al-Bahr al-Ra'iq, 1/71; al-Sharh al-Saghir, 1/23; al-Majmu, 2/56; al-Muhadhdhab, 1/5; al-Mughni, 1/37).
Third case: water that has met an avoidable pure substance, like saffron or soap, one of whose attributes has changed. Is it pure and purifying, or pure without purifying, removing neither ritual impurity nor filth? Two opinions.
First opinion: the water remains pure and purifying. This is the view of the Hanafis and of Ahmad in one narration; Shaykh al-Islam Ibn Taymiyya declares it correct (Majmu al-Fatawa, 21/25). Their evidence: the general verse:
"If you find no water, then perform tayammum"
Surah an-Nisa, 43
This verse covers all water: the word "water" there is indefinite in a negative sentence, and the indefinite in the context of negation is general: tayammum is therefore not permitted while this water exists (al-Mughni, 1/36). Then the hadith of the man whom his camel gored and killed:
Wash him with water and sidr.
authentic hadith, reported by al-Bukhari and Muslim
Had it not been purifying water, the command to wash with it would be empty: a dead person is washed only with water with which ablution is valid. This water remained water: it kept its name, its fluidity and its flow, and resembles water thickened by grease (Tabyin al-Haqa'iq, 1/21; al-Bahr al-Ra'iq, 1/71; Hashiyat at-Tahtawi, 1/18; Sharh Fayd al-Qadir, 1/72; al-Mughni, 1/36). It is also reported from Umm Hani (may Allah be pleased with her):
The Messenger of Allah (peace and blessings of Allah be upon him) washed himself, along with Maymuna, with the water of a single vessel: a bowl in which traces of dough remained.
authentic hadith: reported by Ibn Majah (1/37), an-Nasa'i in al-Kubra (242), al-Bayhaqi in al-Sunan al-Kubra (1/17) and Ibn Hibban in his Sahih (1245)
Second opinion: the water is pure without being purifying, like meat or broad bean water; it is used for ordinary purposes, cooking and the like, but not for ablution or ghusl. This is the madhhab of the Malikis, Shafi'is and Hanbalis. Abu Bakr ibn al-Hasan ibn Abdallah al-Kishnawi the Maliki, author of As'hal al-Madarak, writes: water changed by a pure substance, like milk, is pure in itself without being purifying; it is used for ordinary purposes, cooking and drinking, and not for acts of worship, ablution and ghusl (As'hal al-Madarak, 1/38; Mawahib al-Jalil, 1/59). An-Nawawi says: what we have mentioned, preventing purification with water changed by mixing with a non-purifying substance while other water exists, is our madhhab, the madhhab of Malik and of Dawud, and likewise that of Ahmad in the more authentic of the two narrations. Abu Hanifa moreover says: purification is valid with water that saffron has changed, and with every pure substance, whether the change be small or great, on condition that the water flows, not that it be thick, with the exception of meat broth and broad bean broth (al-Majmu, 2/59-60). Their evidence: this water has changed through contact with an avoidable, non-purifying substance: ablution is therefore not valid with it, as with boiled meat water; and mixing with an avoidable pure substance, like saffron, removes its unrestricted character: one who has sworn never to drink water therefore cannot drink this water (al-Mughni, 1/36; al-Insaf, 1/32).
Fourth case: water changed by mere proximity to a pure substance, like grease, or to solid pure substances like agarwood and camphor, so long as they do not dissolve in the water and do not rot in it. The Hanafis, Hanbalis, some Malikis and the most apparent view among the Shafi'is hold it pure and purifying: the change comes from proximity alone, and does not prevent the water from bearing its name, like water varied by a nearby scent (Tabyin al-Haqa'iq, 1/20; al-Sharh al-Saghir, 1/22; Hashiyat al-Dasuqi, 1/59; al-Hawi al-Kabir, 1/52-53; al-Muhadhdhab, 1/5; al-Majmu, 2/61; Sharh al-Minhaj, 1/19; al-Mughni ma'a al-Sharh, 1/38). The Malikis according to the soundest view among them, and the Shafi'is against the most apparent view, hold it pure without being purifying, by analogy with saffron-mixed water (Hashiyat al-Dasuqi, 1/59; al-Sharh al-Saghir, 1/22; al-Hawi al-Kabir, 1/52-53; al-Muhadhdhab, 1/5; al-Majmu, 2/61; Sharh al-Minhaj, 1/19; al-Mughni ma'a al-Sharh, 1/38). Ibn Qudama specifies: if the neighbouring substance perishes in the water or rots in it, the water takes the ruling of pure water that does not purify: ritual impurity is no longer removed with it. He writes: what changes water by proximity without mixing, grease of every kind and solid pure substances like agarwood, camphor and amber, so long as it does not perish in the water and rot in it, does not remove the water from its unrestricted character: it is a change of proximity, as if a fragrant thing swayed beside it; we know of no divergence on this. Tar, bitumen and wax follow grease: they change the water by their greasy nature, without preventing it from purifying (al-Mughni, 1/38).
Water mixed with an impurity divides into 2: water in which one attribute has changed, and water in which nothing has changed.
The first: the scholars agree that it is impure. Ibn al-Mundhir says: the scholars agree that water, little or abundant, into which an impurity falls that changes its taste, colour or smell, is impure as long as that lasts (al-Ijma, 21; Majmu al-Fatawa, 21/30).
The second gives rise to 2 opinions:
The first opinion invokes the hadith of Abu Sa'id al-Khudri: the Prophet (peace and blessings of Allah be upon him) was asked about performing ablution with the well of Buda'a, into which menstrual cloths, dog meat and putrid things were thrown; the floods carried them there from roads and courtyards, without anyone throwing them in deliberately. He replied:
Water is purifying: nothing makes it impure.
authentic hadith: reported by Abu Dawud (66), at-Tirmidhi (66, graded good), ash-Shafi'i in his Musnad (1/165), Ahmad in his Musnad (3/31 and 86), Ibn al-Jarud (47) and al-Bayhaqi in al-Sunan al-Kubra (1/4), among others; Ahmad, Ibn Ma'in, Ibn Hazm and Ibn al-Jawzi authenticated it (see Talkhis al-Habir, 1/12; Tanqih al-Tahqiq, 1/29)
This text is general: it covers little water and abundant water, and all impurities (Majmu al-Fatawa, 21/33). Al-Dasuqi notes: if a tiny impurity, a drop, falls into a little water, a quantity equal to a vessel of wudu or ghusl or less, without changing it, its use is disliked for removing ritual impurity, for treating filth, or for anything that depends on purifying water, such as recommended or meritorious ablutions and ghusls; for ordinary purposes, there is no dislike. The dislike is subject to 7 conditions:
The holders of the second opinion diverge on the boundary between little and much: 3 definitions.
The Hanafis: water that blends with itself, one end moving when the other moves, is of little quantity; water that does not blend this way is abundant: an impurity falling into it does not make it impure. Its surface measure: 10 cubits by 10 cubits; below that, it becomes impure even without a visible trace of impurity and, if flowing, with an apparent trace. The trace is taste, colour or smell, for they do not persist with the flow; and its depth must be such that the bottom does not appear when one scoops. On the meaning of internal blending, al-Kasani reports: the transmissions agree that it is reckoned by movement: if moving one end moves the other end, the water blends; the manner of moving is disputed: Abu Yusuf narrates from Abu Hanifa movement by washing without force; Muhammad, by wudu; a narration, by hand, without washing or wudu. As for the great pond, whose ends do not transmit movement to each other: if the impurity falls on one side, ablution is valid from the other side, the impurity apparently not reaching it (Bada'i al-Sana'i, 1/252-253; Mukhtasar al-Quduri, 13).
Their evidence: the hadith of Abu Hurayra:
When one of you wakes from sleep, let him not dip his hand into the vessel before washing it 3 times: he does not know where his hand spent the night.
reported by Muslim (87)
If the water of the vessel were not made impure by dipping, the prohibition, based on fear of impurity, would be meaningless; yet water moved by a limb from one end carries the movement to the other. The reports are also abundant on washing the vessel licked by a dog, with no change of colour, taste or smell (Bada'i al-Sana'i, 1/251; Tuhfat al-Fuqaha, 1/56; Mukhtasar al-Quduri, 13).
Malik ties quantity to change: water whose colour, taste or smell changes is of little quantity; water that does not change is abundant (Bidayat al-Mujtahid, 1/46; al-Sharh al-Kabir, 1/71).
The Shafi'is and Hanbalis: water that reaches 2 qullas is abundant, otherwise it is little. Their evidence: the hadith of Ibn 'Umar: the Prophet (peace and blessings of Allah be upon him) was asked about water in the desert frequented by wild beasts and livestock:
If the water is 2 qullas, it does not carry impurity; and in a narration: nothing makes it impure.
authentic hadith: reported by an-Nasa'i (1/46), Abu Dawud (63 and 64), at-Tirmidhi (67), Ibn Majah (517), Ahmad (2/27), al-Darimi (731), al-Hakim in al-Mustadrak (1/224, authentic by the condition of the 2 shaykhs, adh-Dhahabi concurred), al-Bayhaqi in al-Kubra (1/261), al-Daraqutni (1/19-20); Ibn Hibban authenticated it (1245), al-Albani authenticated it in Sahih Sunan Abi Dawud (56), and an-Nawawi graded it good in al-Majmu (2/70)
Ibn Qudama says: its definition by the 2 qullas indicates that what is below them becomes impure: had the 2 qullas and what is below them had the same ruling, the definition would be empty (al-Mughni, 1/52). Al-Shirazi says: the 2 qullas can be protected from impurity in vessels, abundant water cannot: so they are made the dividing boundary (al-Majmu, 2/70). Ibn Hajar specifies: "it does not carry impurity" means it is not made impure by the impurity that falls into it, as the other narration, reported by Abu Dawud and Ibn Hibban, explains.
Used water, called "musta'mal", received different definitions from the companions of Abu Hanifa, and a status that diverges from one school to another: pure without purifying for the majority, purifying in one narration of Ahmad, treated with precise detail among the Shafi'is.
Among the Hanafis: for Abu Hanifa and Abu Yusuf, used water is water removed after a ritual impurity or a bodily use made in seeking nearness to Allah, such as wudu repeated with the intention of drawing near or of discharging an obligation; for Muhammad ibn al-Hasan, water employed to establish nearness; for Zufar, water employed to remove a ritual impurity. The madhhab: water becomes used the moment it separates from the body (Fath al-Qadir, 1/86-90; Tabyin al-Haqa'iq, 1/24; al-Hidaya Sharh al-Bidaya, 1/20; Mukhtasar al-Quduri, 13; al-Bahr al-Ra'iq, 1/103; see Fath al-Bari, 1/355 and 414; Ahkam al-Quran of al-Jassas, 5/210). The effect of these definitions appears in 4 situations:
Used water among the Hanafis does not purify from ritual impurity, but does so for filth according to the soundest view: a real impurity can be removed with it (Bada'i al-Sana'i, 1/244; Hashiyat Ibn Abidin, 1/348 and 353; Mukhtasar al-Quduri, 13). Ibn Hajar reports in Fath al-Bari (1/355): the one who said used water is impure was Abu Yusuf; ash-Shafi'i reports in al-Umm, from Muhammad ibn al-Hasan, that Abu Yusuf retracted and then returned to it 2 months later; and 3 narrations come from Abu Hanifa: pure without being purifying, the narration of Muhammad ibn al-Hasan and the key of the madhhab; lightly impure, the narration of Abu Yusuf; grossly impure.
Among the Shafi'is: used water is water of little quantity employed in fulfilling the obligation of purification from ritual impurity, like the first washing, or in removing filth from the body or garment. As for supererogatory purification, renewing wudu, the 2nd and 3rd washings, two views exist: the correct one, according to an-Nawawi, is that this water is not used, and it is the apparent text of ash-Shafi'i (al-Majmu Sharh al-Muhadhdhab, 2/139; al-Muhadhdhab, 1/8; Rawdat al-Talibin, 1/138). All agree: the water of the 4th washing is not used, that washing not being supererogatory (al-Majmu, 2/139). Al-Dardir specifies, for the Malikis: little water employed to remove ritual impurity, then employed again for ritual impurity, is disliked under 3 conditions: being of little quantity, having served to remove ritual impurity and not filth, and the second use also aiming at ritual impurity (al-Sharh al-Saghir with Bughyat al-Salik, 1/27-28). Ahmad al-Sawi draws from it: water employed for filth is not disliked for ritual impurity, and water employed for ritual impurity is not disliked for filth (Bughyat al-Salik, 1/26).
The Shafi'is distinguish little water, below 2 qullas, from abundant water. The correct view of the madhhab: little used water is pure in itself: the righteous predecessors did not guard against it, nor against what dripped from them. From Jabir ibn Abdillah (may Allah be pleased with him):
The Messenger of Allah (peace and blessings of Allah be upon him) came to visit me while I was ill and unconscious; he performed wudu and poured over me the water of his wudu, and I regained consciousness.
reported by al-Bukhari (194) and Muslim (161)
But it is not purifying: it removes neither ritual impurity nor filth; the predecessors, with little water, did not collect used water but turned to tayammum, and they did not drink it, for it is revolting. If it is collected fresh and reaches 2 qullas, it becomes purifying again according to the more correct view: impurity is stronger than use, and impure water, collected until it reaches 2 qullas without change, becomes purifying with certainty; used water deserves this all the more. The opposite view: it does not become purifying again, its strength being consumed by use: this is the choice of Ibn Surayj (Mughni al-Muhtaj, 1/82-83; al-Majmu, 2/138 and 142). Al-Shirbini notes: the reason for the prohibition was debated; the more correct: this water is no longer "mutlaq", as an-Nawawi and others held (Mughni al-Muhtaj, 1/82-83; al-Majmu, 2/138 and 142). Al-Hisni adds in Kifayat al-Akhyar (54): the correct view is that an obligation was fulfilled with it; it is said: an act of worship; the stakes appear in 2 cases: water employed in supererogatory purification, renewing wudu, recommended ghusls, the 2nd and 3rd washings, remains purifying according to the correct view, no obligation having been fulfilled with it, and does not purify according to the weak view, an act of worship having been fulfilled with it; and the water with which a woman of the Book washed herself from menstruation in order to become permissible to her Muslim husband: if she converts, is the washing required of her again? According to the more correct view, yes; and the water she used while an unbeliever follows the reason adopted: obligation fulfilled, the water does not purify; worship fulfilled, it does, the unbeliever not belonging to the people of worship.
Al-Shirazi summarizes in al-Muhadhdhab: used water is of 2 kinds: used for purifying from ritual impurity, and used for purifying from filth. That of ritual impurity is pure: pure water has met a pure place, like washing a pure garment. May one purify oneself with it? Two paths among our companions: the stated text: no, its unrestricted character has been withdrawn, like water that saffron has changed; and a narration reported from him: yes, use has not changed the water, like washing a pure garment; some companions do not authenticate this narration. That of filth: if it separates from the place while changing, it is impure, according to the saying of the Prophet:
Water is not made impure by anything except what changes its taste or smell.
reported by Ibn Majah (521), at-Tabarani in al-Kabir (8/104) and al-Daraqutni in his Sunan (1/28); an-Nawawi grades it weak: Ibn Majah and al-Bayhaqi reported it from Abu Umama with taste, smell and colour, and all graded it weak; ash-Shafi'i reported its weakness from the people of hadith, and al-Bayhaqi demonstrated its weakness; the argument then reverts to consensus, as al-Bayhaqi and other imams said, and ash-Shafi'i hinted at it: this hadith is not established, the people of hadith have no like of it, but it is the view of the generality: I know of no divergence among them (al-Majmu, 2/69)
If it does not change, 3 views: pure, the view of Abu al-'Abbas and Abu Ishaq: water that cannot be protected from impurity does not become impure without change, like abundant water into which an impurity falls; impure, the view of Abu al-Qasim al-Anmati: a little water has met an impurity, as if the impurity had fallen into it; and the view of Abu al-'Abbas Ibn al-Qass: if it separates and the place is pure, it is pure; if it separates and the place is impure, it is impure: the separated water is part of the water remaining in place, and its ruling follows it (al-Muhadhdhab, 1/8; al-Majmu, 2/139-140).
Among the Hanbalis: the apparent text of the madhhab: water employed to remove ritual impurity, with no attribute changing, is pure without being purifying: it removes neither ritual impurity nor filth. Another narration from Ahmad: it is pure and purifying, removing ritual impurity and filth: a pure place was washed with it, its purifying character never ceased, like washing a garment; it met a pure place and does not leave its ruling through repeated use, like the garment in which one prays repeatedly. This second narration is the view of al-Hasan, 'Ata', an-Nakha'i, az-Zuhri, Mak-hul and the literalists, the second narration of Malik, the second view of ash-Shafi'i, and the choice of Shaykh al-Islam Ibn Taymiyya (Majmu al-Fatawa, 20/519) and Ibn al-Mundhir; see al-Awsat, 1/285 and 288; al-Mughni, 1/46; it is also the view of 'Ali ibn Abi Talib, Ibn 'Umar and Abu Umama.
As for water employed in meritorious, non-obligatory purification: renewing wudu, the 2nd and 3rd washings, the ghusl of Friday and the 2 festivals: 2 narrations: like water of ritual impurity, the purification being legislated; or with no effect on its purifying character, the person not being prevented from praying, like cooling water: if the purification is not legislated, using the water changes nothing, like the 4th washing of wudu. Ibn Qudama writes: no disagreement: water used for cooling and cleaning remains in its unrestricted character; we know of no divergence (al-Mughni, 1/46).
Water employed in an act of worship without ritual impurity, such as washing the hands upon waking at night: if that washing is not obligatory, its use does not affect the water; if it is, then according to al-Qadi, the water is pure without purifying. Abu al-Khattab reports 2 narrations on it: it loses its unrestricted character, being used in worship, like water of ritual impurity, the Prophet having forbidden the one who rises at night to dip his hand into the vessel before washing it: proof that it produces an impediment; or it remains unrestricted, no ritual impurity having been removed, like cooling water (al-Mughni, 1/43 and 46). In summary: the Hanafis and Shafi'is, along with a narration from Ahmad, hold that wudu water employed once is not valid for a second, and that whoever used it must repeat indefinitely: it is not mutlaq water, and one who finds only it performs tayammum. Malik: ablution is not valid with it if other water exists, and he said: there is no good in it; without other water, he performs wudu with it, without tayammum: it is pure water, nothing has changed it. Ahmad, second narration: it is pure and purifying, wudu is valid with it. Water for cooling and cleaning remains unrestricted: purification with it is valid without divergence among the jurists (al-Tamhid, 4/42-43; al-Awsat, 1/285; Nayl al-Awtar, 1/63; al-Mughni, 1/46). Ibn Hajar further cites, in Fath al-Bari (1/414), the hadith of Abu Hurayra: "let none of you urinate in stagnant water nor perform ghusl from major impurity in it"; he was asked: how then? he replied: he draws from it; the prohibition of immersion aims to keep the water from becoming used to the point of depriving others of its benefit: one of the strongest proofs that used water does not purify.
The common foundation remains: mutlaq water without alteration purifies without discussion; alteration by an avoidable pure substance and prior use in ablution are the 2 points where the schools part ways. When in doubt about a particular water, the way common to the 4 madhhabs is to look for other water, and to turn to tayammum if none is found; to settle a precise case, a scholar will rely on the opinions and references given here.