sewerage system fosse

[eabadger]

Not sure if this will be of any interest, but we as a family are currently renovating and converting an old stone property in northern France.
So far we have done all the work ourselves with no external help, just lots of research and a fare few mistakes! we are not builders, but thought, "how hard can it be"?
When we bought the place, which consisted of 1 small derelict cottage and a large oak framed barn and stone stable, our first priority was a sewerage system whilst living part time on site, being English, I got hung up on emptying contents of chemical loo, even on our own land, in a deep, straw filled hole.
So in 2008 we made the decision to buy a secondhand mini digger off ebay and build a Fosse Toutes eaux, this is the standard type of system in France, it is estimated that 75% of France if off grid as far as sewerage at least, many old properties have straight septic tanks, that should be emptied by a licensed company, every two years I think, but many old soles have bashed a hole in the side, or get the farmer to remove when required, didn’t want this, and we were paranoid that we would be arrested for poisoning the environment.

So in the summer of 2008 we arrived, armed with a mini digger and a plan from the local body who licence these things, SPANC, yes, I know!
First thing we need to buy all the “bits”, but from where, we visited all the local builders merchants, but they only sold the concrete tanks, we didn’t want this, mainly due to it have once chance of going in, after the man with lorry/hiab arrived, if our hole wasn’t finished we were scuppered.
So a large 6000ltr plastic tank was needed, ok, equivalent of b&q, Brico Marche, very helpful chap, could order one, but due to it being august, could not get it delivered from head office for at least two weeks, not good news, I had just over that time to do all install and finish.
So back home to think, driving home we noticed Xavier, one of our neighbors house, a house still not completed, we went for a nosy, yes he was installing a fosse, all we had to do was speak to him and find out where he bought it.
Knock on his door, Xavier and his father in law were inside this, building site, ushered in I was offered drinks, a common and none negotiable thing here, and not tea.
So some hours later I stumbled home down the lane, with the information required.

The next day I drove back to the b&q equivalent, but then drove a further 100mtrs, to the factory that make the fosse, and all the ancillaries, bought all that was required, put in trailer and returned home.

The build was sort of straight forward, lots of doubt that it would pass certification, but it did, and the system seems to work well, with no smell.
We have to feed it bacteria and watch what is put down it, but on the whole very pleased with it, from what we hear, this system is the EU standard, never heard of its use in the UK, hence the post, if anyone wants more info, please let me know.

[eabadger]

Looking back, one of the issues was disposing of the spoil, in all we had 3 artic full lorries of stone, so spoil was maybe 100T, had some stone over we did the road.
We had to leave trenches open for inspector.
And i needed some help, so taught my son how to load me up with stone, couldn’t get lorry down the lane, so tipped about 200mtrs from where we were working.

[EccentricAnomaly]

Interesting. I know little about these things and need to know more. In what way is this different from a septic tank? Is it that the solids get fully digested then released into the leech field? Isn't that how a lot of people use septic tanks in practice: i.e., if you somewhat oversize them/don't use them to full capacity then they don't fill with solids so don't actually ever need emptying? Does this scheme just make that practice official or is there something else involved?

[eabadger]

Hello, I am by no means an authority on these, just glad that not only can we be off grid with power and fresh water, but also with sewerage.
Aim is me an clan move to house when ready, grow what we can, forage as well, note large wood at our side, free to roam.

From what I read the breakdown of the solids takes place by two different types of bacteria, one at the bottom of the tank (the solids) one at the top (the fats and scum).
I understand the top layer becomes solids, and then drops to be munched on by the bottom bugs.
A swirl effect also breaks up solids, until particles become small enough to become floating matter, they then exit through a removable volcanic rock filter.
After leaving the tank the liquid enters the filter field, which is either sand or stone, a test prior to installation decides this, the man testing the soil also has to provide details of depth of cleaning media, amount of trenches and tank size.
Our system is a 6000ltr tank, 4 x 17mtr trenches, this will be for both our main dwelling 6 bedrooms ish when finished, and the small two bedroom cottage for visiting relatives.

So to the trenches, total depth just over 1.2mtrs, these after excavation are filled with 30mm down granite, on top of this is laid the pipe which I am told is like soak away pipe, 100mm diameter with slots cut in one side.
All entries to top of pipes must be perfectly level, giving fluid equal chance of going down all, without favoring the fist nearest inlet, however I am skeptical that in practice these remain so for long.
All of the pipes are connected at the exit end, with an inspection point, basically any liquid in here, your pipes/filter bed is blocked.
The waterborne solids when exiting the pipes get lodged in the stone chipping, another bath full of water comes along breaking down the solids more and more.

We use the correct cleaning and washing products so as not to kill our bacteria culture, which is fed once a week by something that looks like and could be a form of yeast.
If anyone using system has a prescription of antibiotic the system must be force started, instead of one small packet of bacteria, a whole box..
The system is now connected to two toilet and a bath, we also have a washing machine, and have had up to 11 people staying at one time, the cost we were quoted for this to be done was about €7,000.00 we spent that ourselves and had to do all the hard work, but now own our digger outright and have the satisfaction of having done it ourselves. 

We created a road to our place after this project, and then replaced the roof and all the timbers, currently installing the windows and shutters, and at the same time digging out the floors, have removed from one room, about 3 ton of stone, will have to mix onsite all concrete as no access to lorries now, I think that will be a bigger job than all the rest we have done to date?
Picture shows what will be a pantry on rear wall, and front dining room, the external and internal walls are all minimum 700mm solid stone, lime rubble infill.
We already have the UFH system onsite along with a air to water heat pump, not sure about this yet, bought it without too much research. As you may be able to see in pictures, we are next to a large woodland, and have ability to buy wood and drag home, so main heating will be wood, as I said the air source jobby, and a backup of a diesel system, in France all heating, oil that is, is diesel based, so old Aga’s wont work, only pressure jet systems, I want to have something that can be just put on at a flick of a switch

[titan]

They look the same principal as a typical UK septic tank except they use a filter arrangement instead of a twin tank  http://www.bioassainissement.com/8.html  the diagram shows the solids on the bottom of the tank which will need to be emptied as normal. The biggest problem as explained to me by a real expert ( the guy who co- wrote the BRE off mains sewage  papers) is there is no way of ensuring the pipe in the filter beds remains level and water will take the lowest route missing most of the field which then becomes blocked sooner. He recommended that I have two parallel trenches and the ability two alternate between them on a yearly basis allowing the resting trench to recover. I did a little spreadsheet application that will calculate   leachfield sizes from BS 6297 based on your percolation test results which anyone can have a copy of. The French love their Fosse Septic tablets but they are generally not needed. I don't think I would want to put excessive fats into any off mains system tank and would use an inline fat trap before the tank if a lot of fat is used in the building,  a lot of cooking for example.

[eabadger]

Yes I agree about settlement.
I did tend to poo poo (pardon the pun) the general French systems, but in hindsight, they have been doing these for years, 75% not on mains sewage.
We have run without the bacteria powder and with it, and it does smell without it in, and water coming out of tank in to field is clearer with it in, less oily.
Septic tanks under EU law it would appear are a no no, and who wants to have them emptied?
From what I have learnt from the SPANC inspector, this will need emptying of real solids, non biological, every 10 years or so.
I did enquire about the pipes clogging, and was told they have an expected life of 25 years+, we have inspection points at each filter pipe head, and one inspection at end, solids of any description getting this far is slim, and those that do get bashed up by the bath being emptied, the principal is simple, and again I am no expert, but did fit it easily and have lived with it, and real world tests are always best, or at least in my opinion.
From what I understand fats are part of the whole process, if the tank is to be sites more than 10mtrs from the house, then grease traps must be installed

Other things I used to poo poo in france were, electricity supplies, but they have some good ideas, your mains tariff is based on maximum power supply, you can go for 2.2kv upwards, the lower the power the cheaper the tariff, why, well less supply needed on the whole, in the uk, we have to have a 60a or is 100a supply for each house, and do we ever use this? From what I understand in the uk a housing estate must be able to supply all properties with maximum rating at once, is this true?
Also ring mains are illegal in France, again at first I was of the opinion why, they are the best, but having had it explained to me, we in the uk are the ones in the past.

Also forgot to add, we have to cover all pipes in anti leaching fabric, to stop soil ingress into filter beds, the head end pictures shows corner of inspection chamber with each bed fed from a different port, so can easily see issues before they are problems, I suppose I could then flush pipe through, but again, by the filter bed point, the floating material is very, very small.

[eabadger]

Titan, just read you link, yes that about covers it, but the solids are broken down, not static, that is the point of the bacteria, without appearing lude, if a dog does apoo outside, eventualy rain action breaks it down and returns it to nature, same principal in this the water entering first part of tank bashs up solids and they are then eaten by the bacteria, if you look on the link you posted you will see the final filter on the tank outlet, a bag of volcanic rock, stops the solids leaving until broken down, you are advised to agitae this every 6 months or so, or simply replace, very cheap.
again fat shown on top is part of the self eating process.
the solids that remain are things that should not have been put down the low in the first place!

anyway each to there own, a good friend of mine is building off grid in Spain, and is using fig tree's, apprently fig trees thrive on human waste, no i dont accept his kind offer of fresh figs!
but in reality he will be putting in one of these toute eaux, not sure of spanish name.

[Baz]

In Africa we had a very successful bannana tree growing beside the septic tank.
In the UK, before being forced onto mains about 50 yeas ago the pipe just went down the field a bit and stopped in the boggy bit. Mum wouldn't let us play in the boggy bit for some reason.

[eabadger]

do you think that is where the word bog came from?
mums are so unfare!

[titan]

I did tend to poo poo (pardon the pun) the general French systems, but in hindsight, they have been doing these for years, 75% not on mains sewage.

Septic tanks under EU law it would appear are a no no, and who wants to have them emptied?

From what I have learnt from the SPANC inspector, this will need emptying of real solids, non biological, every 10 years or so.

I did enquire about the pipes clogging, and was told they have an expected life of 25 years+,


Also ring mains are illegal in France, again at first I was of the opinion why, they are the best, but having had it explained to me, we in the uk are the ones in the past.

The French have been doing it badly for 75 years and the local mayors  have been told to sort it out. I have had a place in France ( the Creuse ) since 1996 and helped  working  on a few French septic tanks where previously they were  never emptied so just put raw sewage into the local water course. The system you have is a septic tank, I think the design to include a tank filter is quite clever as it  ensures you can't ignore it when it starts to clog unlike a single or even a double tank system. Septic tanks were shown by the BRE to give the best overall treatment of sewage and are not as far as I know banned in the UK, cesspools are.  The tank will need emptying according to it's size and use which will  vary. If there were some magic enzymes or bacteria I am sure we would know about them here.   I wouldn't want to dig up my leach field after 25 years doesn't sound like very long to me. I don't think ring mains are from the past, You could always wire your house in the UK radially if you wanted to. In 40 years of travelling and sometimes living there I would take UK electrical standards over French anytime. It is only relatively recently  they have started to bother getting the polarity the right way round and the first thing I would do is check if there is an effective earth as they quite often seem to be token gesture. I love France and the French by the way.

[eabadger]

hi titan,
I made the comments about ring mains, and i am 16th qualified, the 17th was going to outlaw rings, but in the end left it for the 18th. Polarity, do you mean live and neutral?
Ac mains supply alternates, no polarity.
Neutral will be effectively earthed at sub or dis point.
Most properties in France have earth stakes, these the French care for, and even water, the brits ignore and have problems.
My local hardware store sells various different earth stakes depending on your soil type location etc.

Ring mains and why they are bad;
If you drill a hole in your wall at home and hit the ring main, bang goes the trip, opps, you reset trip, all seems ok, but ring is no longer complete, big problem depending on what load you are putting on end nearest break, with picture now hanging on wall, who would ever find break.
Also in UK you mention earth, well in UK the conductor for earth doesn’t have to match cross section of mains conductor, so if you do have a problem?
All cross sections in France must match, be the same size.

Look any country where the people rise up and say no, we don’t agree gets my vote.


not sure why you mention 75 years, maybe i missed somthing? 100's of years maybe.

like i said each to there own, i have received loads of advice from brits in france, some who have been friends for years, and most of it has been rubbish, when in rome!

information below;

The secondary part of this system is a filter bed that treats all the water removing solids and pathogens’ and then disburses the ‘purified’ water back to the ground.

Once the waste and water are in the tank they start to divide.The lightest parts such as fats, oils and grease float to the surface where they form a crust called Suspended Solids. This crust is digested by aerobic bacteria and converted into water and Carbon dioxide.

Heavier solids settle at the bottom of the tank forming what is called ‘The Sludge’. Like the crust the sludge is digested by bacteria, only this bacteria is Anaerobic. The liquid remains between these two layers slowly circulating.

Pre-treatment removes approximately 30% of the pollutants and the remaining 70% contains germs and pathogens which pose serious health risks if untreated. The remaining waste undergoes the ‘Treatment’ stage by passing from the tank and through the filter bed where once processed it is discharged back in to surrounding land where finally nature will purify the water fully and it will pass back in to the ground water to be used another day.

Many installations in France (Estimated at 75% of rural properties) do not comply with current regulations and hence European Law has forced the French government to take action to bring all installations up to standard. There is currently inspections happening in areas of the Vendee where all Fosses will be inspected and brought up to spec.

The regulations on the construction of Fosse Toutes Eaux are tough, and as of the 3rd January 1992 all towns and villages in France had their responsibilities increased and the Maire is now responsible for all aspects of wastewater treatment and is directly responsible for the control and regular maintenance of all installations in their area.

[titan]

hi titan,
I made the comments about ring mains, and i am 16th qualified, the 17th was going to outlaw rings, but in the end left it for the 18th. Polarity, do you mean live and neutral?
Ac mains supply alternates, no polarity.
Neutral will be effectively earthed at sub or dis point.
Most properties in France have earth stakes, these the French care for, and even water, the brits ignore and have problems.
My local hardware store sells various different earth stakes depending on your soil type location etc.


Ring mains and why they are bad;
If you drill a hole in your wall at home and hit the ring main, bang goes the trip, opps, you reset trip, all seems ok, but ring is no longer complete, big problem depending on what load you are putting on end nearest break, with picture now hanging on wall, who would ever find break.
Also in UK you mention earth, well in UK the conductor for earth doesn’t have to match cross section of mains conductor, so if you do have a problem?
All cross sections in France must match, be the same size.

By polarity I meant phase and neutral,  you say  you have  TN−C−S earthing and then TT earthing they aren't comparable but being an electrician I am sure you know what you are talking about. Regarding the earth rods if they have to water them why would they not use TN_C_S if EDF provides it.

Ring mains and why they are bad;
If you drill a hole in your wall at home and hit the ring main, bang goes the trip, opps, you reset trip, all seems ok, but ring is no longer complete, big problem depending on what load you are putting on end nearest break, with picture now hanging on wall, who would ever find break.

Also in UK you mention earth, well in UK the conductor for earth doesn’t have to match cross section of mains conductor, so if you do have a problem

Not sure what you mean here but if the circuit is broken wouldn't the ECBO sense the imbalance and not reset. Also I thought the  earth wire in a modern installation is more for tripping the Current sensing  safety devices I don't think it is designed to take any significant current.

not sure why you mention 75 years, maybe i missed somthing? 100's of years maybe.


The secondary part of this system is a filter bed that treats all the water removing solids and pathogens’ and then disburses the ‘purified’ water back to the ground.

75 years was my mistake, I misread 75% .  The bit of your reply in bold describes the action of a septic tank, they all need filter beds although in France they seem to miss this bit occasionally.

I am sorry if you think I am being critical of your system, I am not but it is just a septic tank nothing more. There are only three options for off mains treatment, a cesspool, just a tank that collects the wastes and need emptying often, a septic tank which separates solids and has some biological breakdown then discharges the liquor for secondary treatment with filtration via either  a leachfield or reedbed and finally a mini treatment plant either with added oxygen or a Klargester BioDisc where the liquor can be discharged direct without further treatment. In France and to a lesser extent in the UK a septic tank may have just  been a vessel to hold solids with holes or very short drain runs for the liquid to escape.

Good luck with your French adventure


I have part TN-C-S and TT earthing and a septic tank on the house I am currently building and spent a lot of time researching off mains sewage treatment to find the best system. Although I didn't ask ask friends as they know sod all about it.

[eabadger]

Titan,
I was merely letting other know what I had done, and looking at all different things is how we learn, I don’t think you are critical of our venture, it is after all the only one that would pass the SPANC exam, I cant believe they are called that.
All I can say is what I find, for us it has worked well, I believe from friends further south that sand filters are not good, but our stone one is fine, or so far.

No I am not an electrician (electronics engineer), I do employ many, and did all the exams so could be one, but theory is just that theory.
Watering of earth stakes is the norm if weather is dry, we used to tip water on a stake to get a better earth reading, now we test other things, that we do leak tests on, the insulation breaks down, so when we test in summer my engineers throw water over them to test real style, with a mega.
TT systems are as you may know preferable in telecoms installation, but also as majority of France is fed overhead, consumer earth is safest, say a tree fell on the overhead and knocked out the conductor and earthed neutral, to the consumer it appears no power but in reality!!!
Also bearing in mind we are all working towards saving energy/planet 1/3 the amount of copper.

You in France all the time?
Trying my hardest to move full time, have been offered a job with a Japanese company in France, what a mix, me, them and them.

now attached my roof, i thought, how hard can it be??