There are some things that make ablution invalid; such as any discharge from private parts and this applies to stool, urine, semen, blood and wind. Also Deep sleep and touching one’s private parts break ablution.

What invalidates the ablution

Ablution may be invalidated by any of five things, as follows:

1-A discharge through one’s private parts. This applies for any discharge of urine, stools, semen, blood or wind, of any amount. In the Qur’anic verse that mentions the situations when ablution becomes required for prayer, 

With regard to a situation when one doubts if one has broken wind, 

2-A discharge of impurity from any part of the body. If the discharge is urine or stools, it certainly invalidates the ablution.

3-Loss of the mental faculty, as in the case of sleep.

On the other hand, madness, drunkenness and loss of consciousness invalidate the ablution according to all scholars. Sleep that invalidates the ablution is deep sleep when the sleeper loses all awareness, no matter in what position one is asleep. Dosing off slightly does not invalidate the ablution.

Many scholars consider that if one sleeps seated in a way that does not allow breaking wind, one’s ablution remains valid.

4-Touching one’s private parts directly, without cover.

5. Eating camel’s meat.