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I thought it might be a good idea to post on the subject of the good old Portuguese fosse 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.
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.
