9. Washing ones mouth in the morning: [1]
Some have the custom to rinse their mouth in the morning to remove the ririm that is found in the mouth, in order to bless the Almighty G-d with holiness and purity. [The Chabad custom is to rinse the mouth prior to reciting the morning blessings.[2] Thus, prior to reciting the blessing of Al Netilas Yadayim over the second morning washing, one is to rinse his mouth, and taking time to do so is not considered an interval between the first washing and the blessing. Some have the custom to rinse the mouth two to three times.[3] Nonetheless, this is only an initial requirement, however, Bedieved, if one said the blessings prior to rinsing his mouth, he fulfills his obligation and is not to repeat the blessing.]
Fast days:[4] On a public fast day one does not rinse his mouth in the morning. [If, however, this is causing one discomfort he may be lenient to rinse his mouth.[5]]
[1] Kama 4:17; Michaber 4:17
[2] Sefer Haminhagim p. 4 [English]; Shaareiy Halacha Uminhag 1:3 as a directive of the Rebbe Rashab
[3] Emek Habracha, brought in Shaareiy Halacha Uminhag ibid
[4] Michaber 567:3; Sefer Haminhagim p. 4 [English]; Ketzos Hashulchan 2 footnote 25 in name of Aterez Zikeinim
[5] M”B 567:11