Some acts are reprehensible when someone is relieving himself such as talking to anyone or to urinate over a crevice in the ground. It is also reprehensible to urinate facing wind direction if it is in an open area.
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.