where do i find out more info on making a check valve

 

just run a vacuum line from the hole that your map is over to the bottom of the map (basically just an extension instead of having the map right on top of the hole), then just cut the vacuum hose, and put check valves in line

 

ok i found a site on how to make it. where do i buy the check valves.

 

from a pet store, they are fish tank valves or something....

 

thanks