Fosse Septic Concrete cover

We have a Fosse with only half of a concrete inspection cover and a damaged surround. As such it filling up with rain water.

We are getting it emptied but need to purchase a new cover. Any ideas where these can be purchased?

As an aside - should this 'water' not drain away - somewhere?

Thanks in advance.

The good news is that he could see an obvious leak. Although he did confirm that it was mostly rain water - so off to get a new cover today.

The grey water doesn't seem to be a blockage - the drainage operative (not sure what to call him) simply said who ever put in the pipe from the grease trap put in too small a pipe.

Fosses toutes eaux are as you say but there is a commune near us that is insisting that is all people may have now. They refuse to allow micro-stations. It is right that rainwater would just be water but why is that banned then the grey water allowed? The logic defies all reason.

It's not just a plastic barrel Mike. A conforming fosse installation these days is the fosse, a second filter/treatment chamber plus the plateau d'infiltration and the various ventilation pipes required. Taking off the VAT and the other taxes that businesses bear there's not a lot left. We had a Biorock treatment filter retrofitted to our existing fosse toutes eaux and that came to around 6K all in all. Best to get another couple of firms to provide a devis though.

David, Thanks for the tip. The levels are far too high and I was focusing on the lack of drainage from the Fosse as opposed to leakage from ground water into the Fosse.

Although we we have only half an concrete inspection lid I also made an assumption that the heavy rain was contributing. ie. Filling the Fosse directly.

I'll ask the chap that empties it today if he can advise.

Up until now we have only used it as a holiday home and I guess by the time we got here, mainly in the spring and Summer, (and lack of usage) this just sorted itself out once the rains had stopped. Now we have moved in we are seeing the real issue.

The loo seems to flush OK but the grey water (Shower, sink etc.) is backing up via the grease trap (which I have cleaned out). Cant find any blockage in the pipes though....

As I said we had a quote to replace and 10,000EUR seemed high for buring a plastic drum with a soak away - but talking to others this is about the going rate?

A thing that bothers me is your description of the level of the surface of your fosse. Basically the inlet for the fosse and the outlet should be at the same level. Thus when you flush the bog the faecal matter sinks to the bottom of the fosse and the transporting water briefly raises the level in the fosse and is decanted through the exit pipe taking with it some of the black water in the fosse. Fosse toutes eaux are not like old septic tanks where the solid faecal matter was prevented from passing to a second chamber by means of a physical barrier these were if you like longitudinately separated. The fosse toutes eaux is horizontally separated but not physically by way of a wall or other partition. The shit goes to the bottom and is digested and the polluted water eventually is decanted through the exit pipe. In a functioning system the inlet and outlet are always more or less at the same level. The situation you describe suggests to me that your fosse septique might have sprung a leak. Check that the level of the contents of the fosse are at the same level as that of the inlet and outlet pipes. If they are not then you may well have a leak and thus the amount of water you have around the fosse


Our tank is well past its sell by date I would suggest (a very old concrete one) - but at !0,000 EUR to replace it might have to last a bit longer.

Pumped out tomorrow and a new cover and that'll do for now. Look to have it replaced in the next or two.

The rain water is not from a roof but just the fact that it had only half a cover with some tarpaulin covering it - I guess with all the rain - our garden is sodden - it has helped top it up.

I am still curious why the water is not draining away from the fosse itself? We also have some backing up to the grease trap. I have put some rods down the pipe and no blockage. Assuming it is to do with how high the fosse is - less than a metre from the top!

Unless that is in these old Fosses the grey water thorough the grease trap does not go direct to the Fosse? then we may have a different issue?

It might be the law now but it is complete madness. Grey water put into a septic tank will contain detergents that counteract the bacterial work that degrades excrement. It will pass through the septic tank unchanged and into the ground. If that is where it is going to end up anyway you might as well put it straight into a soakaway, separate from the tank, with all the grey water and rainfall. The only way around this is legislation forbidding detergents for people with septic tanks and insisting on soap products which are degradable. Just because things are law does not mean that they make sense. As for drainage at the other end of the tank - that is and always has been necessary since septic tanks were invented because the clean water overflow has to go somewhere and the somewhere is into a system of land drains where it soaks away. This is not new, it is historic.

He have a registered ground works company in France and my husband fits fosses for a living. The concrete inspection covers can be purchased from most builders merchants, the price can vary from 20-40 euros. Not sure whether you have an old system or a new one that complies with the new régulations, but according to the new rules your fosse toutes eaux MUST take all the grey water (sink, shower, washing machine etc.), as well as black water. The rain water (from your roof) MUST NOT enter the system. Again, if you have a newish system, you would also have draiange at the other end of the tank. (Unless it is a microstation.)

It depends where the rainwater is coming from. If it is coming off the roof then, ideally, it should be routed to a soakaway, the same as the bathwater and sink water. All that should be going into the septic tank is the foul drain and not rainwater or grey water. The septic tank is there to digest excrement - there is no point flooding it with water as it serves no purpose.

But to answer your question, why do you not cast your own cover ?

We got ours from Big Mat, but any of the building supplies i.e. Leroy Merlin, Socobomat etc., will get them for you.