With H-shem's help, we have begun learning Hilchot Tzitzit with the Ben Ish Chai, Hacham Yosef Hayyim of Baghdad. The sefer is translated by Shmuel Hiley and published by Yeshivath Ahavath Shalom Publications in Jerusalem 5765/2005. He calls the names of the Chapters by the names of Parashiot, so instead of Chapter One, the first chapter is called Parashath Bereshith, Laws of Ziziyoth. Please note these are for learning purposes only. For the halacha lemaaseh, i.e. for what to do yourself please ask your own Rav.
Parashath Bereshith, Laws of Ziziyoth, Page 6
9. One should not remove the tallith qatan at any time, even when one goes to sleep, or has intercourse; it may only be removed when one takes a bath or immerses oneself in a miqveh. If one enters a lavatory without another garment over the tallith qatan, one should tuck away the ziziyoth, so that they do not remain revealed there.
This learning should be in memory of Maran, HaRav HaGaon Ovadia Yosef, ztz'l.