Draining a Wash Basin in the Basement
I’ve recently bought a house that I’m remodeling. The plumbing was done by the person I bought the house from but it has not seen water until yesterday. I added a slop sink in the basement and drained it into a pre-existing caped end that was there. After having the water turned on yesterday I checked all the sinks to make sure they worked properly and they all drained without causing me a reason for concern. Including the slop sink. I then filled the tub on the second floor to check for leaks there. Upon draining it I heard water running in the basement and found the slop sink overflowing, filling from the drain. After the tub was complete drained the slop sink stopped overflowing and started draining. At a relatively slow rate I would say. I’m wondering if there is a blockage between the house and the main sewer or is the slop sink not vented properly?
In the basement there is a 3” or 4” line that runs from the ceiling down into the basement floor. Approximately 18” above the basement floor there is a reducing tee with a side entry of 2 inches. This line has a tee in it with one leg going straight up into ceiling creating what I would assume is the venting system for the house and the other leg of the tee goes to a short run of pipe and then the cap that I removed to install the slop sink drain. This 18” above floor line is lower than the sink bottom but higher that the slop sink drain trap.
I hope I’ve given you enough information to answer my question as to whether this system is vented proper?