Musty toilet water/mildew smell from downstairs bathroom

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Sunday Gladiator

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San Diego

Just joined this forum. I registered mainly because I was inspired by this thread here -

I've run into a similar issue with my downstairs guest bathroom, which is just a toilet and sink next to it. The issue has persisted for a full year now - best way to describe it is a pervasive musty, toilety, mildewy water smell coming from this bathroom. Not sewage smell, but a musty old water smell.

We've stopped using the toilet and sink for several weeks now. Whenever we run the showers or sinks in the upstairs bathroom, the smell kicks in (my wife smells it the strongest). The smell then comes from the upstairs bathrooms, and emanates from the downstairs bathroom too.

Here's what's been done thus far, and the timeline of attempted fixes -

> Checked all traps in downstairs sinks, including this bathroom. Cleaned out traps, made sure water was in p traps than air for one week. Smell continued.

> Replaced the Kohler toilet with the Toto Drake® II Two-Piece Toilet, 1.28 GPF. Wax ring replaced in the installation. Smell continued.

> Ran cameras in our sewer line from outside clean out. Ran camera all throughout the lateral line, that goes past our downstairs bathroom, lateral pipe then makes a turn under living room, then down all the way to the street level sewer line. All clear. But... minor 'calcification' in the pipe just behind where the lateral line goes past the downstairs bathroom. Sewer line camera tech said it's minor, and in his opinion, not a cause for concern or smell. Decided not to flush lateral pipe. Smell continued.

> Opened up walls in downstairs bathroom to expose vent pipes. Ran smoke test from outside clean out to check vent pipes. No sign of smoke from vent pipes, both at toilet and downstairs sink. Nor upstairs. Nothing. But... after capping the final 3rd vent pipe in attic, a tiny funnel of smoke appeared at the edge of the closet flange in downstairs bathroom's toilet! The plumber then stuffed rags tight and deep into the pipe past the flange to check to see if there was a crack or leak past the concrete and towards the lateral line. Ran smoke test again. No sign of smoke. New closet flange put in and sealed. Rags removed. Ran smoke test again. No smoke! Toto toilet re-installed.

> Next day, no smell! Hooray. Toilet used and sink used.

> Day two, smell came creeping back, but not coming from toilet. This time same ol musty/mildewy smell coming from downstairs sink. Proceeded to stop using downstairs sink and toilet. Smell continued.

> From day three to today - 2 weeks later. Smell continues in downstairs bathroom, and upstairs whenever showers or sinks are used. A musty/mildewy water smell coming from downstair bathroom sink.

Next steps I am thinking -

> Have plumber run enzyme based cleaner (not Drano!) down into ALL showers and sinks upstairs and downstairs.

> Remove downstairs bathroom toilet and have Sewer Line Camera tech run a camera through toilet and to the lateral line to run a leak detection. Try and check for any cracks in pipe (I was told this was a difficult detection, only leaks can be detected).

That's where I am today. Quite the short story saga. :) Any further insights or investigations I should do beyond the above, I'm all ears!

Thanks, Parker
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