Help with CO2

Im currentley experimenting with a coal power plant useing the Refined power mod. I currently have 16 mk1 coal burners running at full power producing 30/min of CO2 they are all ran into a single Mk2 pipe with no valves and routed to the roof where i have 4 CO2 towers consuming 150/min. All other gases such as steam is being processed correctly and the only bottle necks in those pipes is when the CO2 backs up. I am using mk1 pipes to come out of the machines but then they all merge into a mk2 pipe The burners are in green and the CO2 takes the route in red to the roof there are 3 Mk1 pumps on the right side behind the wall to assist the CO2 in reaching the roof, according to my math i am producing 480/min of CO2 and have the capacity to get rid of 600/min. But my pipes are constantly full and not transporting the CO2 too the roof. Any ideas or solutions will be greatly appreciated