We are often asked if it is necessary to run separate vent lines for each condensate return unit in a multiple unit system. Large systems or multi-zone systems often make individual venting impractical. There are no industry standards for sizing condensate return vent manifolds, but ASME Controls and Safety Devices for Automatically Fired Boilers (CSD-1) guidelines for manifolding gas pressure relief valves can safely be applied. click here to learn more.