From About This Project
Under every drain in your house, there’s a trap that holds water and prevents sewer gas from flowing up into the air you breathe. But if you have a shower that’s been abandoned since the kids moved out or a floor drain that never gets used, the water in the trap can eventually evaporate. That lets in stinky—or even dangerous—sewer gases. The solution is a few ounces of cooking oil. Dump a bucket of water down the drain to refill the trap. Then add the oil. The floating oil forms a seal over the water and prevents evaporation—without raising your cholesterol.
Fats and oils are bad for septic systems. Everyone knows that you shouldn't put these things down the drain if you aren't hooked up to town sewer. Can anyone comment on a tank-friendly alternative?