septic gas in the house

There is septic gas in my friend's house. First was noticed when family members moved in temporarily and began using the basement bath and shower when it is normally hardly used. They pumped the aerator septic system and odor didn't go away. There is no water on the concrete floor indicating a break. There are two vents - the north vent also drains the master and guest bathrooms on the main floor of the ranch and the laundry in the basement. The south vent also drains the kitchen and the basement bathroom. Upon investigation, I have found there is water in the south vent, and no odor comes out it on the roof, and the toilet gurgles and bubbles and the water in the bowl goes up and down. I snaked the shower, but ran out of snake and might have run into stuff because I would feed it, it would stop and then I would auger and it would pull it on down and then stop and repeat. I might get a bigger snake. I snaked the toilet without any difficulty - it just pushed right through.

Is the basement slab uncovered anywhere? Can you see any signs of dampness there? Is the water in the sump hole smelly? You may have a broken or dislodged drain line under the slab.

Most of the slab is covered with carpet or linoleum, about a 1/5th is uncovered. I will check that, happen to be going over there tonight. The sump hole smells pretty much like just a sump hole, damp, a little musty, nothing out of the ordinary. The septic did need pumped, I guess it was full, and that was done. It's funny how it just started to do that. I'm going to check with them, but it seemed like when they had a number of things running water, it really kicked up. The house is probably 50 years old. Thanks for your response, I will check these things out.

Just came from this house and there are no signs of moisture coming through the concrete in the open areas and nothing observable in the carpeted areas. The guest told me that when the washing machine was draining several times during the day he noticed an increase in the odor. The laundry room, as I have described, is below two bathrooms on the main floor and they share the same soil vent pipe. When I was there, the odor was strongest in a small room south of the basement bathroom and I know there is a vent pipe from the bathroom that runs over that ceiling somewhere and then turns up and goes out the roof. Sure could use your thoughts on this or how to isolate the source.

Even though there's a vent, it doesn't mean that things are vented properly.

Well, it has all worked for years, except that the basement shower was hardly ever used, and now, it seems that the odor is made stronger when the washer discharges. I'm going to check out the vent from the roof for blockage. The odor seems to come from the room south of the basement bath where i suspect the vent runs horizontal for a point and then turns up. What other things can be tried to locate this problem. Looking for ideas. Thanks

Thanks, I will check that. but also, reread the initial post as I have changed it with new information.

A couple of ideas of things to check if not of the more obviously/likely pans out...

Is there a fan in the bathroom with the shower that could be drawing bad air from somewhere?

Does the house have air conditioning? If so does the condensate drain into a drain or vent?

You should not be able to see any standing water in a vent. Could have something caught in there: squirrel, bird, bird's nest, rat, etc.

Thanks for your reply. That is one of the things I've been thinking and tomorrow I am going to make access to the vent and cut it in the basement and see what happens. I'm going to drill a hole to release any water into a bucket and then cut it and snake it from that point. I will keep you informed.

Bluebinky, thanks for looking into this, but "no" there isn't a fan, and I don't know about the condensate, but will check it out. What does it mean if the condensate does? Thanks

When you drain the HVAC condensate line into the sewer line (drain line), depending on the season, the trap of the thing can dry out. Say you have an a/c unit, and drain it into the sewer via a trap. Over the winter, the trap dries out, then you have a direct path for the heating system's blower to blow sewer gasses into the house.

I have both a condensing boiler and central a/c. Each has condensation outlets. Many would tie them together, but my a/c was in first, so I just ran a drain outside, thus no connection to the sewer. But, the boiler runs in the winter...not viable to run that condensate outside as it would freeze up and create a skating rink! So, it gets dumped into my washing machine stand pipe.

For many, gravity venting the a/c condensate outside may not be possible, and it needs to either be pumped somewhere or drained into the sewer system. It should go through a trap, but as mentioned, over the heating season, that trap will usually dry out, leaving an opening for the system's internal blower to suck sewer gasses into the HVAC system for distribution into the house.

If this is a problem, the solution is to either dump it into a trap that gets more use and thus won't dry out (such as the washing machine), or to periodically dump some water down to keep the trap full and thus block the connection for sewer gas.

Jadnashua, that is good info, and I will check that. I saw the line going into a trap, but didn't check the trap. What does it do? Does the furnace suck the gas through the condensate tube from the dry trap - is that what you're saying? Also, new information: I got snookered - the south vent has water in it alright - here is what it looks like since I had to remove some things to find it - the vent comes down from the roof 14' to the ceiling of the basement and then it does a 90! for about 5' and that 5' is slanted back toward the vertical so water that is in it - maybe from rain? - cannot totally drain out. But still, I think the problem is drainage downline where my snake couldn't reach. Today, I ran a bunch of water from a 1st floor shower and then the basement shower, nothing really was happening, so I filled up the washer with soap bubbles and drained it, within 10 - 15 minutes the sump pump began working like crazy and it had the bubbles in it. During this time the basement shower drain would go up and down with water even to spewing a 3" geyser, there was standing water in it, and the toilet bowl water was also going up and down. Once I shut the water off to the showers, after 10 - 15 minutes the sump began calming down and the shower drained. What does this sound like? Thanks to all.

Sounds like you have at least two problems...the vent needs slope just like a drain line - it should not have water in it; sounds like there's a break in the drain pipe and it's flowing into the sump.

Yep, I think so. It is what I was trying to put off by checking everything else. I will let you know. Thanks