Smells from Bathroom drains

Hello all,

my home was built in 2004 so not that old of a home and we have been here about 5 years. My master bathroom has a double sink setup. for some time, we have noticed the sulfury or sewage smell emanating from the drains.

The smell is not all the time. If we are gone for a few days and come home, the bathroom smells like it was attacked by fart bandits while we were away. When home, it is not a constant smell. It only occurs a minute or so after we turn the water on in the sink. Not sure it applies to my home but Googling the issue returned the possibility that there is some sort of "seal" in the line that shrinks when water is not keeping it wet, so when we are away and possibly why it smells when we initially turn the sink water on as well as it is hitting that and bringing the smell out. i dont know....

I have taken out the pipes on both sinks and cleaned them thoroughly, thinking that is where the issue was but its not...

what can i do to get this issue under control?

Thanks

 

Trap seal loss can occur

1- capillary action (action)

2- evaporation

3- negative pressure / back pressure

4- trap not set level

There are two more ways but they would be obvious

 

Smelly bathroom might be due to blocked drain. Try using drain cleaning solutions.

 

Trap "seal" just means water in your ptrap. The water in your ptrap of any drain in the house will evaporate when no water in put in it for several days. Just like if you left a glass of water sit in the counter for several days. The water that sits in the U of the ptraps blocks air from coming out of the drain. They call this a "seal" .but it's just water.
This will cause sewer gas to enter house from that drain. So when you leave town for a few days plug your stopper on your sink to prevent this evaporation.
Now to fix your smelly sink drains, mix a gallon of 1 part bleach and 3 parts water. Get your self a funnel and pour it down the overflow hole on your sink. Let it sit for 1 hour. Then rinse it out with regular water. Then remove your ptraps, and pop up assemblys in both sinks. Clean really good in the ridge where the pop up assemblys sit. That is probably where your smell is coming from. Clean that area well, and flush out the overflow hole in your sink the best you can also to try to get rid of the slime and bacteria that has worked it's way up. Then install NEW pop up assemblys and NEW ptraps. This should take care of the issue. Unless your roof vent is plugged or your sinks are not vented and the traps are getting sucked dry of water. While possible, it's very highly unlikely that this is the case, and you would also hear the sinks gurgeling when you flushed the toilet if that was the case.