Question 556: Can you please let us know those things that invalidate Wudhu (ablution) and their Causes?
Brief answer 556: Things that invalidate wudu are: Passing of urine. Excretion. Passing wind from the rear. A sleep, deep enough to restrict sight and hearing. However, if the eyes do not see anything, but the ears can hear, Wudhu does not become void. Things on account of which a person loses his sensibility, like insanity, intoxication or unconsciousness. Istihaza which will be dealt with later. Janabat, and, as a recommended precaution, every state which requires Ghusl.
Detailed answer 556: There are several Unclean Things which invalidate wudu (ablution) and cause the necessity for its repetition.
1 & 2: Effusion of urine or what falls under its category, such as the suspected wetness coming out before istibrã’ or excretion of feces from the natural or unnatural passage, regardless whether the natural passage is blocked or not, and whether its amount is large or small, and whether it is accompanied, for example, by worms or lumps.
3: Passing out of wind from anus, if it comes out of the stomach or bowels, whether it is accompanied with sound and bad odor or not. But the wind that comes out of the front organ (vulva) of a woman, and not from the stomach or bowels is like the wind that enters from outside and then comes out. (It will not nullify ablution).
4: A sleep which overwhelms the senses of sight and hearing (as a result of which the eyes do not see, and the ears do not hear).
5: Everything which stuns human reason such as insanity, swooning, drunkenness or the like.
6: The minor or medium Istihädah (undue menstruation), rather to be more cautious, the abundant one too, though we have declared ritual bath to be obligatory in such cases.
Note: If the water of enema comes out without being accompanied by something like it would not invalidate ablution.
Likewise, if there is suspicion of the water of enema being accompanied by something, Or when some worm or lump comes out without being sullied by feces, (the ablution shall not be void)
 . Tawzih al-Masael of maraja’ (annotated by Imam Khomeini), Vol. 1, Pg. 188.
 . Tahrir al-Wasilah of Imam Khomeini, Vol. 1, Things that invalidate Ablution & Their Causes.