We live in a beautiful 30 y old house, excellent build quality, bricks & cement. 4 similar build houses nearby. Strange is that no cesspool has ever been emptied in the last 30 years, according to owners & neighbors. No one knows of a sewer. We may be sitting on an underground waste Lake. So far no sweat. But recently a slight odor after heavy rain. Manageable with room spray so far.

But want to go after the source.

Any ideas where to dig first?

follow the pipes?

Very logical IMHO but we have just finished a major renovation including tiling a marble floor. How to follow the pipes without breaking up everything?

Toilet is against an outside wall?

Dig outside and follow the pipe outside.

I've also noticed in some older buildings (shophouses) that access to the septic tank can be via a 7 or 8" round metal plate positioned inside the building in the floor near a ground floor bathroom/toilet. A really wonderful design idea where the honey truck has to drag a long smelly hose through the building to empty the septic tank.

No sh..house outside, three bathrooms over 2 stories. Neither has the honey truck man been able to detect anything where he could drag his long smelly hose to nor anyone of the neighbors

You might try running water down drains that haven't been used for a while. If they are trapped, that will for sure help, but not a bad idea in any case.

Your garden may be the sewer! Or it could simply be the septic tank vent isn't high enough!

No 7-8" round metal plate on any of the floors?

No sewer lines visible exiting the building?

No odd metal ventpipes anywhere on the property?

No meter-sized cement caps?

No large green plants doing very very well only in one specific spot?

If it were me I might get so curious as to pop a toiled and fish a metal tape down the line and follow along with a metal detector above ground.

Then again, I'm not that curious and would probably just suddenly decide to move somewhere else when the toilet finally chooses to back up.

From the OP opening remarks you do have a "cesspoool". Actually it's most liokely a spetic tank and if installed properly it doesn't have to be pumped very often, I'm working on 16 years. But eventually it will fill, up with non degragable solid wastes and could be causing your problem. Before I start digging and breaking things up to "follow the pipe" I would have it pumped. It's not expensive. Where I live in the "boonies", it's 100 baht/hole.

Wayned. The point is the OP can't seem to find the septic tank.

Wayned that might be it. You gave me idea to have the pump attached to the seldom used former servant's squat toilet. If something goes wrong there damage control would be easier than in the living quarters. Or how would you do it.?

I think what he means is to pump out the tank that is underground somewhere. I don't think the companies can run their hose through a toilet - but who knows? Do you have anything you could use to spike into the soil (like a piece of re-bar) and just poke around your yard? It "should" be within a few meters of at least one of the toilets. Or, maybe contact one of the trucks and see if they can find it.

My wife had the cheapest and perfect solution. Between the floors is a pipe shaft running with a small maintenance door. She put a sheet of self-adhesive Zeitplan film ( for wrapping food stuff) over the door. Totally invisible and odor free. Thanks to all of you

Um....

If all you were worried about was the smell, then I guess congratulations are in order... You solved that problem.

But I don't think that resolves the other issue you uncovered; not knowing how the greywater or blackwater is managed.

If the surrounding soil is the standard Thai clay then probably no drainage/leach field and using a common 3-5 cement rings as a leach tank that, if properly managed, should give you 5-10 years service between honeybucket purges.

While you may not WANT to know the how and where, it's probably a good idea to know so if/when it needs to be serviced you at least have a clue.

Rich, not that I like what I hear but running away from the truth never helps. So the most difficult task will be to idetify someone who know what he is doing. Should be someone who is familiar with construction methods at that time , i.e. 1970-1980.

Thanks for the PUSH