What invalidates ablution
The actions that invalidates ablution differs depending on the School of Fiqh (madh'hab).
According to Abu Hanifah 
, which is the Hanafi School, the following will invalidate ablution:
- Anything that exits from the private parts, such as urine, even if it not customary such as a worm or stones.
- The flowing of any ritually impure substance (such as blood or pus) from a wound (or other opening) to any place that requires cleaning (i.e. it flowed beyond its point of exit), or if it came out with enough force to flow (but was prevent from flowing because it was wiped or absorbed by a bandage).
- Vomit that is a mouthful, such that one would not have been able to keep it in without difficulty, except if it is just phlegm.
- Blood (from the mouth or throat) that overcomes one's saliva or equals it (if closer to red, wudu is invalidated; if closer to yellow, it is not).
- The sleep of one whose rear is not firmly seated. As for the one whose rear is firmly seated, his ablution is not nullified by sleep, even if leaning against something (such as a stick) in a way that if it were removed he would fall.
- Becoming mad invalidates ablution.
- Becoming drunk invalidates ablution.
- The laughter of an aware adult person a prayer that contains bowing and prostration, even for the one praying by head motions alone. If the laughter occurs after the tashahhud, the ablution is nullified, though not the prayer.
- Direct contact of a male private part and a female private part