If some pork falls into water and none of its characteristics are changed

Firstly:

It is not clear to us how the tap water could be contaminated
with impurities of pork origin. What appears to be the case is that such a
thing cannot really happen; rather it is merely whispers from the Shaytaan
to which the questioner has fallen prey.

What the one who is faced with such whispers must do is
ignore them and not give his mind free rein to follow them; he should
remember Allah, may He be exalted, a great deal, call upon Him and seek
refuge with Him from the accursed Shaytaan. If he continues to give free
rein to those whispers, the Shaytaan will gain power over him and will
corrupt all his affairs, and he will begin to doubt everything around him,
and will be in a state of constant anxiety, distress and confusion.

Moreover, we also advise you most emphatically to go to a
trustworthy specialist doctor, for compulsive thoughts and whispers are a
sickness like any other, and needs medical pharmaceutical treatment as well
as behavioural therapy under the supervision of a trustworthy specialist.

For more information, please see the answer to question no.
62839

Secondly: if we assume that what the questioner mentioned is
correct, and that there is some kind of impurity (from a pork source or
otherwise) that fell into a tank of water, but the water was not changed by
that impurity, then the water remains pure and it is permissible to drink
it, use it and do wudoo’ with it.

The Messenger (blessings and peace of Allah be upon him) was
asked about doing wudoo’ with water from the well of Budaa‘ah even though
the flesh of dead dogs and other kinds of impurities and putrid things were
thrown into it, and he said: “Water is pure and is not rendered impure by
anything.” Narrated by an-Nasaa’i (326);classed as saheeh by al-Albaani in
Saheeh al-Jaami‘ (1925).

So long as the water has not been changed by the impurity,
then it remains pure.

Shaykh al-Islam Ibn Taymiyah (may Allah have mercy on him)
said: This wording is general in meaning and includes both small amounts and
large amounts; it is general in meaning and applies to all kinds of impurity
and contamination.

End quote from Majmoo‘ al-Fataawa (21/33).

Ibn al-Qayyim (may Allah have mercy on him) said in his
commentary on as-Sunan (1/83):

The fact that he did wudoo’ from the well of Budaa‘ah, even
though its condition was as they said, indicates that water is not rendered
impure by impurity falling into it, so long as it does not change. End
quote.

It says in Fataawa al-Lajnah ad-Daa’imah (vol. 1,
5/84):

The basic principle with regard to water is that it is pure,
but if its colour, taste or odour is changed by some impurity, then it
becomes impure, regardless of whether it is a small or great amount. But if
the impurity does not change it, then it remains pure. End quote.

For more information, please see the answer to question no.
224923.

And Allah knows best.