Is it permissible to use the public water supply for washing cars?
Question

                Is it permissible to use the public water supply, on roads and in parks, mosques and government departments, for personal interests such as washing one’s car, or filling bottles with water for later use?
Praise be to Allah.
      The Messenger (blessings and peace of Allah be upon him) 
      said: “The Muslims are partners in three things: herbage, water and fire.”

    Narrated by Abu Dawood (3477); classed as saheeh by al-Albaani 
    in Saheeh Abi Dawood. 

    And he (blessings and peace of Allah be upon him) said: 
    “There should be neither harming nor reciprocating harm.”

    Narrated by Ibn Maajah (2340); classed as saheeh by al-Albaani 
    in Saheeh Ibn Maajah. 

    The water referred to in this hadith is ordinary water that 
    is not under the control of anyone, such as seas, rivers and so on. 

    Al-Kashmiri (may Allah have mercy on him) said in al-‘Urf 
    ash-Shadhi (3/84): 

    There are three categories of water: 

    1.
    Water for which no one has undertaken any work in 
    producing it, such as naturally occurring rivers. In this case it is 
    permissible for anyone to set up a water wheel.

    2.
    Where a group of people dig a small stream. In this case 
    it is permissible to give animals water from it, but it is not permissible 
    to irrigate land from it or to set up a water wheel.

    3.
    Water that is stored in vessels. It is permissible to 
    drink from it and it is permissible to take it by force in the case of 
    necessity. End quote.

    It says in al-Mawsoo‘ah al-Fiqhiyyah (25/376): 

    With regard to water that is stored in vessels and the like, 
    it is the property of the one who placed it in the vessel, according to the 
    consensus of the fuqaha’, and no one has any right to it, because even 
    though water is permissible (to everyone) in principle, that which is 
    permissible (to everyone) may become the property of a particular individual 
    if he seizes it, if it is not the property of anyone else, as in the case of 
    firewood, herbage and game (wild animals that are hunted), and it is 
    permissible to sell it, give it as a gift and give it in charity. 

    The custom in all Muslim lands, and in all historical 
    periods, has been for providers of water to sell water stored in vessels, 
    without anyone objecting to that, so it is not permissible for anyone to 
    take it without the permission of the one who put it in the vessels, except 
    in the case of one who fears that he may die; if someone else has water 
    surplus to his needs, then it is obligatory for him to give it to him, and 
    if he refuses to give it to him, then (the one who is dying of thirst) may 
    fight him for it. End quote. 

    See also: al-Mawsoo‘ah al-Fiqhiyyah (1/79-80); al-Fiqh 
    al-Islami wa Adillatuhu (4/419-420) 

    With regard to public water that is prepared by the state to 
    meet specific needs of the people, such as drinking water and the like, this 
    type is more like water that is provided for charitable purposes, i.e., as a 
    waqf (endowment). Therefore attention should be paid to the specific purpose 
    for which it was allocated, and it should not be used for any other purpose, 
    except in cases where it is usually used for another purpose without any 
    objection, or if one uses only a little, such as is usually overlooked. 

    Shaykh Mustafa ar-Ruhaybaani (may Allah have mercy on him) 
    said: 

    With regard to water that is provided for drinking as an act 
    of charity, it is not permissible to use it for wudoo’ or ghusl, or for 
    cleaning impurities from the body, or any other purpose. 

    End quote from Mataalib Ooli an-Nuha (1/104) 

    He also said: 

    The one who enters the hammam (public baths) should be 
    careful in his use of the water, using only as much as he needs to, because 
    it is privately owned or provided as an act of charity or waqf. Using only 
    what is needed is what is allowed according to sharee‘ah and custom, as is 
    known from traditional practice, especially hot water, because of the effort 
    involved in acquiring it by obtaining fuel and giving wages to workers. A 
    similar case is that of water that is given in charity for the purpose of 
    wudoo’, or ghusl in the case of janaabah (major impurity following sexual 
    activity) or following the cessation of menses or postpartum bleeding (nifaas), 
    or for the removal of impurity: no more should be used than is necessary.

    End quote from Mataalib Ooli an-Nuha (1/189) 

    Shaykh Muhammad ibn ‘Umar al-Jaawi ash-Shaafa‘i (may Allah 
    have mercy on him) said:

    If there is nothing available except water that has been 
    given in charity or as a waqf to be used for purposes other than 
    purification, if it is known that the donor intended people to use it in 
    whatever way is beneficial for them, then he may use it for the purpose of 
    purification, and it is not permissible for him to do tayammum. If he is not 
    sure about that, then he may refer to custom and other indications, and it 
    is not permissible for him to transfer water that was provided for drinking 
    as an act of charity from its place to another place, such as taking it to 
    drink in his house, for example, unless it is known or there is an 
    indication that the donor would allow that.

    End quote from Nihaayat az-Zayn (p. 36) 

    Conclusion: 

    With regard to carrying water in a vessel to serve a need, 
    what appears to be the case is that it is something that is usually 
    overlooked, especially if there is a need similar to that for which the 
    water was given in charity to serve that need and was placed in that public 
    place, or if it is for a need that is more serious than that. 

    With regard to washing cars, it appears that whoever provided 
    the water in that place would not allow that, especially as there is obvious 
    harm that results from washing cars in places other than those that are 
    specifically set aside for that purpose. 

    If those who are in charge of that place allow that, or if 
    custom allows that without any objection, and no obvious harm results from 
    that, then there is nothing wrong with it, in sha Allah. 

    Please see also the answer to question no.
    70274 and 72384 

    And Allah knows best.