This paper describes an architecture to convert Sinhala Unicode text into phonemic specification of pronunciation. The study was mainly focused on disambiguating schwa-/\/ and /a/ vowel epenthesis for consonants, which is one of the significant problems found in Sinhala. This problem has been addressed by formulating a set of rules. The proposed set of rules was tested using 30,000 distinct words obtained from a corpus and compared with the same words manually transcribed to phonemes by an expert. The Grapheme-to-Phoneme (G2P) conversion model achieves 98 % accuracy. .