A. Master plumber Rex Cauldwell responds: You will have two pipes at the top of the sump pit: a high pressure discharge pipe, usually 2 inches in diameter, and a dry vent pipe, usually 2 to 3 inches in diameter. To connect the vent, first try to find a dry vent in the house plumbing and tap into that. If you have none, you take the vent outside and up along the siding. Some people terminate the pipe below the soffit, while others take it through the soffit and go above the roof. I’ve also been known to take it through the floor to an upstairs closet, and then outside and up.
Here’s an idea that is not code approved: Install an automatic mechanical vent (2 or 3 inches in diameter) in place of a fixed vent right at the unit itself. This works in some cases, but not all. Every time the pump kicks on, the vacuum will open the vent and allow air to come in, and no air will escape to the house. Officially, you are not...
to read the full article.