On Jun 28, 4:58*pm, sm_jamieson wrote:
For a combined sewer, why not just put the
roof drainage into the top of the soil pipe, which passes right by the
gutter ? I mean, a 4 inch pipe from the roof must be the best
solution. Even in heavy rain, there would never be enough water from
the roof to prevent venting when the toilet is flushed.

When the soil pipe gets blocked... and it rains...
.... I do not think your toilet bowel will handle the volume...