u/kittymeow97

Looking for some advice from Australian plumbers because we’re struggling to work out where a strong sewer/sewage smell is coming from.
House is only around 2 years old in Brisbane, two storeys.
For the last couple of days we’ve had an intermittent sewer-type smell inside the house. Today it became significantly stronger.
Some details:
Smell is strongest upstairs around the living room/stairwell, rather than inside a bathroom.
It does NOT seem strongest around any particular toilet, basin, shower or floor waste.
All upstairs bathrooms/toilets/taps are regularly used, so I don’t think we’re dealing with an obviously dried-out trap.
I’ve run water through essentially all of the traps.
No obvious gurgling or drainage problems.
Toilets appear to flush normally.
We have an ORG outside. There is water flowing normally through the bottom of it and it isn’t backing up/overflowing.
I’ve checked outside when the smell occurs and can’t smell the same odour outside or around the ORG.
We also have a sewer manhole in the yard, but again the smell seems confined to inside.
Ducted AC has NOT been running when the smell appears.
Interestingly, it seems to happen at approximately the same time in the evening. Yesterday it appeared and disappeared, and tonight it returned much stronger.
The smell seems particularly concentrated around the upstairs living area and top of the stairs.
I’ve had a plumber attend, but because the smell is intermittent it’s proving difficult to identify. He doesn’t currently think it’s simply the vent.
My concern is whether there could be a poorly sealed/disconnected sanitary or vent pipe connection somewhere inside a wall/ceiling/roof cavity, particularly given where the smell is concentrated.
Would a smoke test of the sanitary drainage/vent system be the logical next step?
Are there any other tests you would recommend before opening walls/ceilings?
Also interested to hear from anyone who has diagnosed something similar in a relatively new build. What ended up being the cause?
Trying to approach this systematically rather than getting plumber after plumber out to check the same traps and drains.

Looking for some impartial opinions because I’m getting really frustrated and don’t know if I’m overreacting.
I hired a landscaper for a backyard/front yard project and paid a $3,600 deposit. The total job is around $10,500.
Since starting, progress has been extremely slow. Most days he has only worked for around 2 hours before leaving. There have been repeated reasons for delays, including his car breaking down, supplier issues, and changes to the fence paint colour. Every time I ask for an update, I get another explanation and a new timeline.
The frustrating part is that many of the things he’s said would happen simply haven’t happened. For example:
Work days are often very short (around 2 hours).
The outdoor blinds have been delayed for almost two weeks.
The fence painting had to be redone after the original colour wasn’t right.
The fence installation and other landscaping work haven’t progressed as expected.
I find myself having to ask every day what the plan is.
This morning I simply asked:
“What time are you looking to start today?”
“What’s the plan today? Can you please chase up the outdoor blinds?”
His response started with:
“We just need to relax a tad… I’ve had no car and I’m doing my best…”
I understand things happen, and I’ve tried to be patient, but at this point I’ve lost confidence because the timelines keep changing and the progress doesn’t match what we’ve discussed.
I’m now considering removing the fence installation from his scope and getting another contractor to do it, or possibly ending the arrangement altogether if things don’t improve.
Am I being unreasonable, or would you also be losing confidence at this point?
If you’ve dealt with a similar situation, what would you do?