Sewer gas smell in basement when doing laundry on main floor
Hi. I am in need of serious help. We bought our house 2 years ago as a new build. A few weeks ago, we started to finish the basement and had the rough plumbing put in for a 1/2 bath. Since then sometimes when I do laundry (laundry room on main floor) the basment fills with a strong sewer gas smell and if the furnace kicks on, the whole house smells. The plumbers have been her several times trying to figure out why but have had no luck. This never happened before we started finishing the basement. We have a whole house humidifier hooked to the furnace that was hooked to a little pump that sat on the floor but now they hooked it up to the sump. The sump lid has been sealed with silicone. They vented it through the main vent in the roof. Like I said, it doesn't happen all the time. The plumber said maybe it had to do with the way the wind was blowing at times so I've been trying to figure out if that has anything to do with it. And if so, how I'm supposed to fix it since I can't control the weather. The commode and sink are not installed yet. Would that have anything to do with it? If so, why does it only smell sometimes when I do laundry and not others. Any help would be greatly appreciated. Thanks.
If the drain for the toilet and/or sink is not capped, that is probably where the odor is coming from. Toilet drains do not have traps on them since it would be "double trapped" when the toilet is installed. An open sink (or toilet) drain will allow sewer gas to enter the house. If you have floor drain(s) in the basement, the trap on it could be sucked dry or just dried out. This will also allow sewer gas to enter. The wind blowing would only apply if there was not water in a trap and this would allow the gases to enter. Check these items and let us know.
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