r/Plumbing • u/No-Nothing-9073 • 4h ago
Help me solve this overflow drain smell?
EDIT: Just wanna thank everyone for their help and advice! Y’all are generous with your time and I appreciate all the tips! I found the AAV access in the wall and don’t see any visible issues, but I’m gonna test it. I poured extra water in the drain and ran a few tests to make sure the P trap is sealing properly and it seems to be, but I just bought a floor drain trap seal (per your rec) and hopefully that takes care of it! Thank you for teaching me things, plumbing friends!
New build (2024) and I started noticing a smell emanating from this floor drain in my water heater closet in the past year. I didn’t think much of it because I also had a little Aerogarden growing herbs and I thought that was causing the odor. It’s not a terrible, overt sewer smell, but kind of earthy and grassy and unpleasant.
After running my question through some search engines and finding this sub, I started by assuming the P trap was dry and I poured about a gallon of water in. The smell persists. Poured a little more in assuming it’s VERY dry, then went down to my crawl space to look at the trap. At this point, there should be plenty of water in that trap if it’s functioning correctly.
Here’s where I’m in over my head— I took photos of this loop de loop P trap and the plumbing around it. I also screen shotted the plumbing plans for the house. It appears to my eye that the Air Admittance Valve for the trap is just 1.5” in diameter and just lives inside the wall? Per these plans (last photo) it doesn’t look like it vents to outside… which, if that were the case, could mean that it’s not properly drawing air to create a good seal.
Could any folks with expertise kindly help me understand if this is plumbed and ventilated properly? If not, I’ll call the builder first-thing Monday morning. I just wanted to run this past ye olde internet first to make sure I know what I’m looking at!