Loosen the line @ both ends and give it a good blow with the air hose, prolly crud in it.
Also don't know what kind of filter you have, but some paper ones will not pass water worth a darn if some is in the tank, ya never know if it has been sitting a while.
Also you don't know what might be in the tank, pulled some crazy things out of them over the years from kids toys to sanitary napkins
