Sewer gas smell

Most probably it is because the ventilation pipe on the sink is not exhausting the methane gas properly, so the methane/rotten egg smell is coming out of the drain. Sometimes if vent pipes are not angled properly, the gas/smell will not rise properly. If there is no ventilation pipe hooked up to the sink, you will most probably smell it. Good luck.

If the house has been sitting for a long time, the traps may have dried out and are not stopping the sewer gasses from being trapped back, flush all toilets and run some water in all the sinks and tubs, to refill the p-traps, also don't forget to pour some water down the washer drain pipe. HOPE THIS HELPS...

Freon is odorless. A sewer odor could be caused by an unused sink, tub, or floor drain trap where the water has evaporated. A gas odor is a very serious issue that should be checked immediately by the gas company or the fire department. Gas can seep in from a leak outside the house or accumulate in a wall if a fitting fails.

The smell is sewer gas coming back in the house from the sewer or septic tank ether from a dried out water trap in a floor or fixture drain, or from the roof vent, or a hole or separation in pipe or fitting. Like wax ring under toilet. First pore water down every drain to fill any trap that might have gone dry, then flush toilet or run washer or drain bath tub.This will displace gas in pipe and will cause the smell to increases if there is no smell then the problem is fixed if not check roof vent it may need a charcoal filter on top, There is no water trap on air vent on roof and is an open hole to the sewer or septic, The heating system in the winter or AC in summer will draw the gas inside from the vent.If it is the vent you should be able to smell it from outside. If all tests fails You will need to have a smoke test done. A smoker is set up outside and the line is filled with smoke and will show where gas is coming from. Also it might be a good ideal to check all gas fittings in case it is a gas leak.

Ensure all your additional rough in plumbing is capped, and toilets or sinks that are not used for long periods of time , sometimes p traps may dry up allowing sewer gasses to enter the home so use them once in a while or fill with water once in a while ,same with floor drains. If that isn't it check that you have them installed.

winter (or rather cold weather) can cause fuel leaks, You should go over the fuel system and check all connections and clamps to be properly fitted and secured. Some vehicles are worse about this than others. I have an older Nissan, and there's a saying when it gets closer to Christmas- Tis the season for fuel leaks! Check your hoses.

Sounds like you have an intermittently blocked vent pipe (the one that goes out through your roof). If there is gas pressure in the downstream sewer line and it can't get up through the vent, it could bubble up through your toilet or sinks. I would get up on the roof with a few jugs of powerful drain cleaner and dump them into your vents. You might also run a few dozen gallons of water down those vents after the drain cleaner has had time to work.
Good luck!

Be sure to keep all water traps [in the bathrooms, sinks] thruout the house full of water, if not then you will get a sewer smell coming into the house in the form of an explosive gas...Methane
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jajoy,

Did you connect the sanitary pipe stack to the sewer line that takes away the flushed effluent? Check to see that the pipe is connected, not leaking sewer gas, not plugged up with an animal carcass, and that the pipe extends through your roof three feet past the roof line (keeps smell out of house).