The Catholic Church teaches: Baptism is performed in the most expressive way by triple immersion in the baptismal water. However, from ancient times it has also been able to be conferred by pouring (not sprinkling) the water three times over the candidate's head. In accordance to the command of Jesus Christ in Matthew 28:19-20: "Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the holy Spirit, teaching them to observe all that I have commanded you." Catholics baptize using the words, "[Name], I baptize you in the name of the Father, and of the Son, and of the Holy Spirit." The Catholic Church accepts any baptism from other Christian Church if it was done in this manner. It has been argued by people smarter than me that not only was there not enough fresh water to baptize three thousand people in Jerusalem but there would not have been enough time to baptize all of them by full immersion in one day even though they started in the morning. Could these have been baptized by pouring water over them? For more information, see the Catechism of the Catholic Church, section 1239: http://www.usccb.org/catechism/text/pt2sect2.htm#1239 With love in Christ.