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Q. I am installing an in-floor ejector pump for a basement toilet. Obviously, a wet vent is not possible, since I don’t want any upstairs fixtures discharging into the sump pit. How do I vent the toilet?

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 supposed to do this because allegedly the mechanical vent does not respond fast enough to the pump.

Incidentally, basement ejector pumps do not have to be installed in the concrete floor. Kits are available which allow an above-floor installation.

Venting a Basement Toilet

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