I have a 400 ft well cased with sealed top 4 ft under ground 3- 90's 1 vent=1 electric=1 water. 4 bolts on cap ....Have air in my lines, pump seems to work fine every thing works right just have very fine air bublbles in water,also have a very dark black substance in my filters have to change once a week .not sure what to do to fix this issue.