nasty smell

[Marie]

Help - we appear to have a nasty smell (so my latest renters have texted to tell me), in one of our bedrooms. The room is the one nearest to the septic tank, so I had the tank emptied last week.  The smell went for 36 hours, but then came back again.  The vent pipe from the tank does go up through this room, but we've put so much mastic & expanding foam around the joints, I don't see how anything can escape from there. There are no boggy areas around the tank, and when we were there last weekend, there was no smell outside the house.  According to the builders plans, there shouldn't be any pipes running underneath this room, so what can be causing the smell??

Any ideas or suggestions as to what I should do next? I'm dreading the phone ringing, as the new renters arrive today, and I thought we'd solved the problem when the tank was emptied.

I've also posted this in the house renovations topic, in the hope that someone will come up with a solution, as I have no idea what can be causing the smell.

Marie

[Maddie]

Have you refreshed your bacteria and how often do you do it?  It needs to be done regularly - more often if there's more waste going into the fosse.  Have your renters used forbidden non-French products or is there a blockage?  Presumably old the old good bacteria went out with the "dirty water" so needs to be topped up to help keep nasty niffs at bay.  Also check that you have water in the traps in showers/sinks etc. (Someone else can probably explain this better).