Sewer Siphon Air Jumper

[stevedeering]

We are evaluating at a large urban sewer system with numerous sanitary sewer siphons. Many of the siphons were installed with no air jumper, or with air jumpers that are too small. In both cases, the sewer atmosphere is sometimes pressurized (probably up to 0.25 inches of water column more or less) on the upstream side of the full pipe sewer siphon causing noxious sewer gases to escape the sewer system and cause numerous odor complaints from the public. Is anyone aware of any standard requirements or rational methods for sizing air jumpers between the upstream and downstream manholes to avoid this problem? The conclusion I am coming to so far, is to make the air jumpers from 1/2 to equal in cross sectional area, as compared to the air space in the upstream sewer during average flow conditions.