mfesharne

Having seen the recent post on getting a fosse emptied I thought it might be a good idea to post a little more on the subject for those that are new to the concept & please note, I've tried to keep it as simple as possible.

A proper fosse (as opposed to a sealed septic tank system) works on the soakaway principle for the liquids & a chemical process to break down the solids & if you find you need to have your fosse emptied on a regular basis, it's probably because it's not working as efficiently as it should.

In short, a fosse is a series of (usually 2 or 3) compartments divided by interior walls that do not quite reach up to the top of the tank & the intention is one compartment will fill & then overflow into the next compartment & then into the next.

The solids should remain in the first compartment & break down by time & chemical process whilst liquids overflow into the 2nd & 3rd compartments and the liquids will then soak away through the bottom of the compartments & through holes in the retaining walls. If the fosse is working correctly, it should rarely if ever need emptying out.

If it does need to be regularly emptied then there's something wrong with it so now let's look at what you can do to improve the efficiency of your fosse.

The things you shouldn't do is use bleach based products when cleaning the toilet & baths etc because it halts the chemical process and prevents the solids breaking down.

You shouldn't flush 'feminine hygiene' or prophylactic products etc because they won't break down & may cause blockages.

you shouldn't use the thicker toilet papers.

You should buy one of the products such as 'Fosse Septique' which is available from Intermarche (If they haven't sold out!) & flush the contents of one sachet down the loo every few weeks. - This restarts the chemical process of breaking down the solids if it has stopped & improves it if it is working.

If you can't buy this or similar products, you can always visit your local fishing shop & buy a small pot of maggots that you then drop into the fosse from the inspection hatch. It's a far more basic solution but it's a solution that's better than no solution.

Some people claim you should only use toilet paper from recycled sources but personally I think that idea doesn't have much merit, however using 2 or 3 ply paper instead of 4 ply and/or quilted toilet paper does usually break down faster.

Now lets look at other factors;

Sometimes the fosse itself can work but the liquids might not be able to soak away properly because of the make up of the soil around it & this was the problem I had with our newly built fosse. The soil around mine was all compacted shale with only about 12 inches of top soil covering it, so I bought in a man with a mini digger & had him dig a coulple of trenches from the wall of the (3rd compartment) of the fosse (towards the top) & sloping down from there for about 6 metres each.

Then I knocked a hole in the wall & pushed the end of some 'land drain' pipe into the hole & lay the rest of it in the trenches. Then we tipped in some gravel & filled in the trenches.

It should be noted that any fosse that hasn't been used for any significant length of time might not work as it should because the solids have hardened & might benefit from an extra 'kick start' with an overdose of this type of products such as 'Fosse Septique' & if you still have problems, the sewage pipes that lead from the house to the fosse might benefit from cleaning & the way to do this is by putting a 'jetter' fitting onto a pressure washer hose & running it through as much of the sewage pipes as you can.

In closing, it took me a couple of years to get mine working as it should & in that interim period I was having to have it emptied every few months but now I've got it working as it should & having installed the land drain pipes, I haven't had it emptied for the last 3 years & don't expect to have it emptied in the foreseeable future.

That's all I can think of for now but hopefully others here can also add their own tips etc.

nogard

Well done; a well written piece.
I am in the process of correcting my fosse. It is a basic two chamber one with no holes twix walls and all the pipes; inlet, vents, outlets etc. in the wrong places and at the incorrect heights.
As you say; not a difficult job.
One tip, to keep it working; fermenting, put in the carcass, guts of any small dead animals you have or come across.
Tip two, run you gray water elsewhere; another tank, a French ditch, reed bed. Gray water will dilute the solution in the main tank.

mfesharne

The guts etc achieves the same thing as either the 'fosse septique' or maggots etc & an old trick is to put a piece of raw meat outside for a few days until it's full of maggots & drop that into the first chamber.

I guess in an ideal world, you'd be able to divert the grey water into or our of the fosse so it has sufficient water to work properly but not more than you need.

It has been suggested on occasion that some people might drop a submersible pump into the final chamber on a rainy night & pump it out onto the nearby fields but of course I don't know if that ever really happens.

EMR

When we first moved into our urbanisation the majority of homes had fossa.
There was a house that we called the " house on poo corner " because that is what they used to do.
Fortunately we were able to connect to mains drainage within a few months.
One day we will get around to having the fossa cleaned , lined and turned into storage for rainwater to use on the garden.

rollermum83

Thank you for all this information, our house has been empty for 2 years and the water from the kitchen and bathroom was being piped down the drain storm at the front of the house, unsure as to whether this was illegal we took this out and piped back into the fosse. We don't put any paper down the toilet, neither do our neighbours, but then they don't add anything into their fosse either. We are having the fosse emptied as we are unsure as to where it goes or what is at the bottom of it, it is based in the garage, we do not have access to the land at the back of the house but my guess is this is where it goes?? . So I guess after all the info we will try with the chemical and see what happens😎

mfesharne

If it's a proper soakaway fosse & it sounds like it is, it'll soakaway from the edges of the brick or concrete walls of the fosse itself but even if you don't have access to the surrounding land it may well be worth asking the owner if you can install the land drain pipe because it'll benefit him as much as it does you........ he'll get the 'enriched water' for his crops whilst you get the benefit of the soakaway.

That is of course assuming the land surrounding your property is farmed & not built on.

rollermum83

Hi yes the land at the back is an orange grove. The owner is just up the hill so should be able to contact him. Thanks😎

mfesharne

Land drain pipe is very flexible so you can even dig the trench around his trees so you won't do any damage...... but don't forget the trench needs to slope downhill from where it enters the top of the fosse.

Pulaski

It's interesting how terminology varies between country, as well as the technology, because what you call a "fosse septique" describe is, more or less a standard septic system here on the east coast of the US.

Our septic tanks (in the US) don't have multiple compartments but they work on a similar principal, with solids sinking to the bottom and slowly rotting, some stuff floating to the top and forming a crust. The overflow pipe is usually passive (no pump) and the inner end of it is bent downwards and drains relatively clear water out of the tank and into the "drain field" which is where the water soaks away. As you describe, you need to be easy on the bleach, use thin toilet paper, don't flush stuff that won't rot, and can buy some sort of enzyme product that is supposed to start or promote the fermentation and rotting process.

This system if properly installed and managed requires very little attention. Ours went about 15 years after the house was built before it was pumped out, and probably didn't really need it, but for less than $200 it was cheap preventative maintenance. Our neighbours went about 20 years before the tank was pumped, but most of that time the house was only occupied by the retired couple who had the house built, but the septic system was sized, per building codes, for a three bedroom house, so 4-5 people. It was also not strictly necessary.

If you own land that is not served by public sewers and you want a permit to build a house you must have a "perc test" (short for percolation), to prove that water can soak away into the ground. Typically if the perc test fails it is because the ground is impermeable clay or there is a high water table.

mfesharne

Fosse is (I believe) the Portuguese word but I think it's the same in French & it refers to an unsealed soakaway......... In English, English it's usually referred to as a sealed septic tank if it's sealed & needs to be pumped out or just septic tank if it's a soakaway but as the man said about the UK & US:

Two nations divided by a common language.

macliam

In Portuguese it's a fossa, not fosse - but obviously the same route. All this talk of "chambers" and things is new - the original was just a hole into which excrement was piped (or tipped) and the liquid soaked into the ground whilst the solids were acted upon by bacteria. They were not sealed and often not even capped - so they were best built downwind. Brick-built and plastic are new versions - better in an area where you have neighbours!