House smells like swamp water

Help Support Plumbing Forums:


New Member
Jan 21, 2021
Reaction score
Hello All, I recently purchased a home with a well and septic system (starting to question this decision). This is all new to me and would appreciate it some of you can answer some questions. Thanks in advance.

I have this stagnant water, swamp, bog type smell in the home that I cannot trace. I suppose it could be a sewer smell, but I have always associated a sewer smell with raw sewage, which is not what this is. I haven’t actually moved in the home yet, but stop by several times a week and notice the smell as soon as I enter. The sellers had a well/septic inspection in October and everything was good as it relates to bacteria, nitrate, etc. I took possession a month later. I’ve also had the septic system pumped.

The smell is fairly faint most of the time, and other times a bit stronger, but always noticeable to some degree. If in the home for some time a while, I kind of forget about it. Kinda like that Febreeze commercial where you can’t smell the odors in your home. But when I I go in the family room it is sometimes stronger there. With the exception of the laundry, that’s the only room that’s underground. The only other odors exist if I use the washing machine. The laundry room turns into a hot bucket of rotten eggs. But no odor in there otherwise.

I’ve tried to trace the smell to the sinks/showers, toilets drains and even the crawl space, which houses the pipes, tankless water heater and pump, but I smell nothing in those areas. On occasion, the kitchen water also has that sulfur smell, but barely noticeable unless you are really sniffing for it.

Any suggestions on what could be the problem will be greatly appreciated. Thanks, Connie

Jeff Handy

Pro Handyman, NOT A Pro Plumber
Jul 5, 2019
Reaction score
Chicago suburbs
There could be a drain trap that has gone dry, letting stink out.

Also, the water heater might be making that sulfur stink.

You might need to change out the anode rode, magnesium rods can cause rotten eggs stink when reacting with well water.

An aluminum/zinc rod will work better with well water.

EDIT OOPS, I missed that you have a tankless water heater.
The smell is still probably coming from the well water.
Sulfur bacteria can colonize the well, and the house plumbing, and release that rotten egg stink as the water hits the air.
The hot water will smell the worst, more volatile and reactive than cold water.
You should contact your local health dept or a local well professional.
Last edited:


Well-Known Member
Oct 26, 2020
Reaction score
It sounds like your water's reaction with the tankless heater. Perhaps getting your water tested for content will be required.


Pump Controls Tech
Lifetime Supporter
Jan 6, 2010
Reaction score
,Lubbock, Texas
You could also have a bad automatic vent in a wall somewhere? I have the same problem with a floor drain. I kept putting water in it to make sure the p-trap wasn't dry. But the well water was letting stuff grow in the p-trap. I pour a little bleach in the floor drain when I smell it now and that works.