We observed four “ water fountain ” sources in the CO J = 3 \rightarrow 2 line emission with the Atacama Submillimeter Telescope Experiment ( ASTE ) 10 m telescope in 2010–2011 .
The water fountain sources are evolved stars that form high-velocity collimated jets traced by H _ { 2 } O maser emission .
The CO line was detected only from IRAS 16342 - 3814 .
The present work confirmed that the ^ { 12 } CO to ^ { 13 } CO line intensity ratio is \sim 1.5 at the systemic velocity .
We discuss the origins of the very low ^ { 12 } CO to ^ { 13 } CO intensity ratio , as possible evidence for the “ hot-bottom burning ” in an oxygen-rich star , and the CO intensity variation in IRAS 16342 - 3814 .