Can’t find Fosse Septique

We are in the process of selling our house which we have had for 20 years - no one can find the fosse - which we’ve never had any problems with ever.The diagnostic report such as it is cost €120 to tell us they can’t find it! Will it be a problem for our sale? Any help appreciated

No pipe with a cap on it sticking up which should have been installed if the fosse was a good 30 years or less? How about following the ground from the kitchen sink, the bathroom or toilet as they must all go into it somewhere and it would not be that far away from the house and usually near enough land for drainage system beyond the fosse if there was room. Do the neighbours know or have the local mairie still got the demand for the permis to install from the fosse installer? Even the local water company may have details, I know they did when we put ours in during 1989. Is there no other item in the ground such as a grease trap or smaller fosse which would both come before the main tank? The problem you have is with SPANC as it may not now conform and they will ask you to sort it out unless your buyer is willing to take the whole thing on but may ask for a reduction in the sellingprice to cover any new installation that will be required.


To save time you must start from a known point which is the house. Looking in the garden is like a needle in a haystack Two things that might help A Metal detector and some metal wire rope. There must be a 4"plastic pipe fitting some where to give access to the system from the house. Thread the rope in and follow the pings. Its know as ping and trace as long as I can remember.
Good luck


Thanks that’s very helpful

which could be in the region of 10k€ for compliance and fees…

No there’ no sign of a pipe there is a small drain like thing outside of the bathroom which occasionally smells so is obviously part of it- very rural area and all the old neighbours have die

Hi and welcome to SF
You could I suppose ask a suitable enterprise to empty/explore the “small drain like thing”. In older properties (like the one we rented some years ago) there was no physical evidence of the fosse outside the property but it was found very close to the house under a gravelled driveway just a few metres away from the house in the direction of the “small drain thing”. It was found to be a small plastic affair under a thick oak board (the size of a door). Once discovered, it was emptied by our local friendly installer and replaced with a concrete one meeting the SPANC requirements. There was absolutely no evidence above ground of its presence.


You are looking for a plastic or cement cover - or just a paving slab to cover the inspection points. They are probably under a massive bush. And by now probably under a foot of soil. It can take forever

Your toilet waste goes somewhere. Follow that internally - it will leave the house at some point. That simply tells you the vague direction to look. Big metal bar and keep jabbing the ground until you find something. Work away from the house. If there’s an inspection port in the toilet waste you can use drrrain rods to find your distances.

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There is a ‘hatch’ ( actually tiles but with a rubber type grout) in the bathroom floor which I think has something to do with it - has anyone got any ideas what it could be?

do you have a cellar? Could the fosse actually be inside the property?

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It may be your septic tank. I have a redundant one in the old outside loo so it may not be current. But equally they were once common and if it works… It’s intriguing you’ve never needed to empty it though - old septics tended to need emptying regularly.

However there still has to be an outlet outdoors if it is active or you’d be swimming in s### after 20 years. But the outlet can be a pipe into a ditch in really old systems.

Equally it sounds like the answer is you don’t have a conforming fosse - if it really is an old septic tank it can’t be made compliant so it’ll be a new one.


I rember trying to find ours, dug holes and with my metal detector found what was a tank lying on its side horizontally. No access plates anywhere no lids just the 105mm pipe going in and a vent pipe coming out above it. The pipe going in was squashed to only around 50mm opening so it would have played up at some point. Mains drainage arrived and went straight passed, it still there and it can stay.
So any vent pipe anywhere?

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My old rental and the old farmhouse which we were gardiens for in the same grounds, neither had a vent pipe visible anywhere…

Neither did my BIL as he mowed them over. No wonder a lot of these fosse dont conform.

If I run the kitchen tap, I can hear the water gurgling outside as it makes its way towards my septic tank. So too from the toilet and the shower room.

Any gurgling outside?

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Hello and welcome… @Nigel57

When you bought your property… even 20 years ago… something should have been mentioned about drains/fosse/whatever.

Check back on the paperwork if you can find it… something should have been mentioned.
possibly just the fact that “it can’t be found but hasn’t caused any problems”… as is the case today from what you are saying…

20 years ago… isn’t that long in the scheme of drains and fosses … someone should know…

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No cellar

Yes I know what you mean the guy whose son we bought it off has died and can’t contact the son- the son had done the DIY on the house himself over a number of years before selling -the hatch in bathroom was all that was mentioned - absolutely nothing about fosse in the paperwork sadly

No vent pipe as far as I can tell - but I am going to have a go with my metal detector too- it’s possible that the fosse is only 22 years old

Not that I’ve noticed but I’ll have a listen next week when we are over