[Cent404]

Hello,

I believe I have a problem:

A sewage ejector pump was installed, the shower, toilet and sink all drain into the pump basin. The underground drain pipes for these fixtures have a vent that ties into the main line that exits the roof.

There is however a second sink that drains directly into the sewage ejector pump's vent (this 2" vent line run to the outside of the house.)

There is now a faint odor, and I believe it is a 'leak' of the gases from the pump basin into the house because of the sink that drains directly into the pump's vent line.

What should I be looking for and is that truly the cause of the problem?

Here is an image of what I am trying to describe:

[speedball1]

What part of "dedicated" didn't the plumber understand when he changed a dedicated sewage ejector pit vent stack into a drainage stack vent with fixtures draining into it. Didn't he realize that this is no ordinary house vent that draws air in. The reason this vent is dedicated is in addition to venting air in as the pump discharges into the sewer it also blows air out as the basement fixtures discharge into the pit. That's right sports fans, you have positive pressure bl,owing sewer gas back into the traps of the fixtures above it. No wonder you have odor.
Call back another plumber to straighten out the mess the first one left you.
Good luck, Tom

[Cent404]

Thanks for your help speedball1, but I don't understand. When the fixtures drain into the basin, they are vented by a 2" pipe that eventually connects to the main vent which leaves the roof of the house. (Is that where it pushes or pulls air ?)

Then there is the 2" vent pipe that comes out of the ejector pump which has a sink (with a U trap) and a hose from a dehumidifier draining into it, this vent goes to the side of the house. (Does this push and pull air as well?)

I'm just not quite sure how to apply your answer, could you explain it in more detail for me?

[speedball1]

When the fixtures drain into the basin, they are vented by a 2" pipe that eventually connects to the main vent which leaves the roof of the house. (Is that where it pushes or pulls air ?)

No! That acts as a regular vent for the basement fixtures. Although you could have connected the upper fixtures to that and wet vented the basement fixtures. The only drawback to that is it would be making the pump work harder.

Then there is the 2" vent pipe that comes out of the ejector pump which has a sink (with a U trap) and a hose from a dehumidifier draining into it, this vent goes to the side of the house. (Does this push and pull air as well?)

BINGO! And every time the fixtures drain into the pit it will blow sewer gas out the dehumidifier drain line right back into your home. It coluld also blow past the sink trap.
There's a reason this line is dedicated. It should leave the house by itself and not be connected to another vent or be used as a drain. A dedicated vent means exactly that.
That vent services the pit and only the pit. I't neither vents or drains anything else. Period!
As I said, Call back another plumber to straighten out the mess the first one left you.
Good luck, Tom