I'm getting a definite sewer odor in my bathroom. It has a toilet, sink and shower. Can't really nail down where it's coming from.

Checked and cleaned the P traps for the shower and the sink. Checked around the toilet flange for evidence of a leak, all dry.

I can see all the plumbing connections from the basement side, no sign of a leak underneath either the shower or the toilet.

Only think I can think of is perhaps the wax seal has dried out enough to allow a gas leak but not liquid. Seems like a stretch to me.

Everything drains nicely, no evidence of a clog or venting issue. Water level in the toilet is normal and still, no evidence of drafts blowing down the vent pipe and the smell is present even on dead calm days. Been going on about a week.

On a septic tank/drain field system. Tank installed ~ 1973, and according to my wife was HUMUNGOUS and she was told "it won't need pumping in your lifetime". I can state with some certainty that it's never been opened. We've kind of been waiting for septic issues on a system that old, but the smell is the only symptom, no evidence of a backup.

Not sure what to check next.

Not a plumber but make sure you don't have a dry trap. If somehow water is leaving a trap the stink will come right up.

Went to a house years ago with the same problem.. bathroom had both a shower and a separate tub.... folks never used the tub... trap was dry...

Assuming the drain traps you have are full I would go ahead and pull the toilet and replace the wax flange.... easy and cheap.... and probably the problem.

quote:

Originally posted by Blume9mm:
Went to a house years ago with the same problem.. bathroom had both a shower and a separate tub.... folks never used the tub... trap was dry...

Assuming the drain traps you have are full I would go ahead and pull the toilet and replace the wax flange.... easy and cheap.... and probably the problem.

This but also check the vent pipe. A lot of them rot out 1-3' above the drain line level.

Dead rodent in the wall? Maybe not a plumbing problem.

If you grab the toilet will it wiggle or move from side to side?
If wax ring is compromised it will stink, especially with a septic system.
Replace wax ring would be my first step.
What are drain pipes back in wall made of? Galvanized pipe can rot off. PVC not so much, but people shoot nails into them putting on baseboard. Also have seen folks put screws or nails into them to hang things.
Start with wax ring.

The toilet is prolly wiggly...if so it’s the wax ring. Go get a new one and replace it.

One a side note if you flush some rid-x down it every month or even yeast it will help digest the poo...you will have no problems with the septic tank. But it should be inspected to see if there is grease floating, if so have that removed.

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Originally posted by rexles:
If you grab the toilet will it wiggle or move from side to side?
If wax ring is compromised it will stink, especially with a septic system.
Replace wax ring would be my first step.
What are drain pipes back in wall made of? Galvanized pipe can rot off. PVC not so much, but people shoot nails into them putting on baseboard. Also have seen folks put screws or nails into them to hang things.
Start with wax ring.

The bathroom was totally remodeled, starting with ripping the floor out right down to the joists and built back up due to years of leaks and rot. I can see the new floor flange from the basement side and it's all PVC over to the old cast iron soil pipe. They connect with a rubber adapter. All solid, no leaks.

The toilet is 100% solid, no wiggle at all, but I'm going to do the wax ring tomorrow because I can't think of anything else it could be. If that doesn't fix it, I'll have to call in the pros.

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Originally posted by jimmy123x:

This but also check the vent pipe. A lot of them rot out 1-3' above the drain line level.

Now THAT makes a lot of sense. The exit on the roof is galvanized pipe and it could well have rotted out. 2-3 feet above where it connects to the main soil pipe would put it right in the corner of the bathroom. There's a 6x6 "box" around it and it runs up the inside of the house, not inside the exterior wall.

I'll get a plumber to run a camera down it, but I bet that's the issue. Never occurred to me. Thanks!

Make sure the vent pipe isn't plugged up with debris.

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Originally posted by ZSMICHAEL:
Dead rodent in the wall? Maybe not a plumbing problem.

Been there. In my case, cause of stench was a dead mouse in the attic near a recessed light in the bathroom.

Could still be a plumbing problem.

quote:

Originally posted by Excam_Man:
Make sure the vent pipe isn't plugged up with debris.

Yea. You can drop a snake down there to make sure it's not clogged.

I'm not a plumber and I'm not saying this is your problem but you might Google something on septic tank pumping frequency. My lovely wife and I have a 750 gallon tank and only us two in the house. I have our system pumped every 4-6 years. The last time it was $200 if I dug the access and $25 more if they dug the access. If the sludge gets to the height of the laterals, you plug the whole field and have a real expensive mess. There are some charts up on the net that discuss whether or not you have a garbage disposal and several other factors which influence the length of time between recommended pump outs. Our house was also built in 1973 and I think ours has been pumped at least 6 times.

Sounds like it could be venting. I had a problem with venting that went through a side wall and a bird decided to try and build a nest. Roof vents can also get blocked.

You said the bathroom was remodeled. Did they by chance install a Studor vent? AAVs can occasionally fail and cause gasses to be released inside.

Thinking more about this last night, now I'm not so sure we've identified the problem.

The upstairs half bath is directly above the downstairs bathroom, offset to one side. The soil pipe is common to both so from the basement to the upstairs bath, it'd all be 4" cast iron and then galvanized pipe for the vent from there.

Wax rings typically do not dry out or shrink. Pipes dropping over decades is perhaps more of an issue but not yours.

A lost trap seal, as noted, is #1 culprit. A forgotten floor or indirect drain. Even a washer standpipe no longer used.

A smoke / fog test would find a cracked stack or other opening.

Another possibility: Wife discovered a bad joint after the P trap on the sink, just before it disappears into the wall.

This was after I'd retired for the evening and she did a "girl fix" on it by wrapping a rag around it. Does seem to have diminished the odor noticeably.

@ Woodman: Thanks, reinforces my thinking.

I'll get some parts today and replace everything from the tail on the sink to the wall connection.

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They connect with a rubber adapter. All solid, no leaks.

Sometimes that is how it looks. An uneven snap or cut, with a Furnco barely grabbing as it should, plus temperature swings, can nudge pipes apart.

An extra wye in line, discovered to be unnecessary (like if it was put in for a double bowl sink but abandoned) and duct-taped rather than properly sealed, is just as likely as a cracked vent stack.

I see you are in Maine. Is you roof top vent pipe frozen over with ice? This happens to us every couple of years.