This is from their site
Setup Instructions:
-Mount the reactor vertically(long side up)
-The water should enter the top and exit the bottom
-Start with the valve closed(parallel to the ground)
-When all the hoses are connected(filter and co2) run the reactor for 24 hours before making any changes
-If after 24 hours you are getting co2 bubbles out of the return pipe, open the valve slightly, then wait for 24 hours
-Repeat the previous step until you are no longer getting co2 bubbles pushed out of the reactor