Need help getting out of problem in new construction project. Please Help!?

Question:Using a water level to measure a pitch of a new sewer pipe, half a bubble would equal what percentage pitch/slope or what fraction of an inch pitch per foot?

Answers:
turn of the bead gives approx 4inches in 20ft level has lines both sides of bead let bubble touch line on high side thats your fall works out half a bubble too much fall