Velocity reducing devices such as an elbow or "T" shall be installed within the distribution box where the effluent line from the septic tank has a slope in excess of 10% or where effluent is being pumped from the septic tank to the distribution box.
N.H. Admin. Code § Env-Wq 1015.02
(See Revision Note at chapter heading for Env-Wq 1000) #9086, eff 2-9-08