There are seven things which make the Wudhu void, some of them which are the most important are:
1. Urinating.
2. Defecating.
3. Passing gas.
4. Sleeping, such that you can't see or hear anything.
source : http://www.maaref-foundation.com
1. Urinating.
2. Defecating.
3. Passing gas.
4. Sleeping, such that you can't see or hear anything.