It is costly for municipalities when sanitary sewer overflow (SSO) occurs. SSO can happen in a residential, commercial or institutional building, as well as in a street or an environmentally sensitive area. The costs of cleaning, damages, noncompliance and possible litigation are daunting. Mechanical inline flapper and swing check valves are sometimes used to stop SSO in gravity sewer lines. However, they have an inherent inability to close off against sewage debris. Also, their high failure rate, frequently required maintenance, high head loss and high cracking pressure make them ineffective solutions. This is why the overwhelming majority of gravity sanitary sewer infrastructures do not use check valves. This paper is a brief discussion of the techniques and use of both duck bill and inline all elastomer check valves to prevent SSO, CSO and sewage back-ups, as well as control inflow and infiltration in gravity sanitary sewer infrastructures and provide odor mitigation.