fosse again

[Dave&Olive]

hi all

        having read all the back posts on fosse went to the mayor to ask for the form for the drainage test ,(trying to save our selves €400 ) he sent us off to the s.v.l you have to go through them so tail between legs of we went .. where do you live said the young lad at svl, Clesse we said , oh you donot need a drainage test in clesse .. YEEEESSS  we thought Great ,simple pipe system will do us land is all sand and rocks we live on a hill elevated from the road yes great...........no he said all new fosse in Clesse the Mayor has decreed must be on a sand filter !!!!

            the 25 cubic metres of land we will have to remove is better than what we are going to have to put back ...

French red tape at its best and do not belive everthing you read on this forum ..every area has its own legal system and laws

dave, olive and 2 cats

[Motorhead]

Well Dave it just goes to show what a truly fascinating subject the fosse septique is.

 

It’s a bit of a common misconception that very well drained soils make a good epandage. Septic systems are 2 stage biological processes. In the tank it is mostly anaerobic but in the epandage it is aerobic. The bacteria there need lots of oxygen to do their work which is why waterlogged conditions are no use but they also need time to do their work which they don’t get if the water doesn’t hang around for long enough. This is probably why you need a sandpit.

 

And yes it does all vary widely from area to area. Where I am the authorities don’t rule out trenches altogether but they do like their sandpits.

[VJ]

First congratulations Motorhead you certainly appear to know your stuff

or B******t baffles brains

can you advise me on some points

1 The second stage of the tank the liquid stage aerobic (you say,) should the liquid from this stage not contain any particulates at all as they will block the soak away?

As this is so surely the sludge level after time will reach a stage where its workings allow particulates to travel over and thereby flowing into the soakaway.

I recall many years ago that the outfeed from the septic tank had a clinker filter that removed any particulates before going into the soak away

The fosse I have currently in France has a plastic bucket with holes in in the top of the second chambre which is at the top before the soak away outlet which does not contain anything and appears to do nothing.

Should this be filled with something to become part of a pre filter or trap?

Many thanks in advance

[Motorhead]

Your bucket is what's known around here as an "indicateur de fonctionment" for some reason that I haven't quite fathomed out yet. It should be filled with a stuff called pouzzolane which is a kind of zeolite (although not the best in my opinion) this helps strain out any particulates and also acts as a (passive) ammonia adsorber. Zeolite can act as an active adsorber in conjunction with aerobic bacteria but there is not enough oxygen for much of that to happen in these conditions. Once it is saturated with ammonia the stuff must be changed or recharged with a brine solution. Pouzzolane is not dear 12.50 euros for 50kg in Brico Depot.

Even with a second tank chamber that is designed keep the water still to promote separation and settling of the solids and the final zeolite filter there will still probably be some solids entering the epandage. These can be divided into the biodegradable and the non-biodegradable. The former don't pose much of a problem unless they get a slime mould growing over them which can block the slits in your pipes. Much worse are the inorganic solids that seem mainly to come from manmade fibres out of the washing machine. These will never break down and are so light they can travel throughout the system. It is probably best practise, especially with a trench system, to get the epandage pipes rodded out every year and the modern systems are designed to facilitate this.

Also I didn't say that the second tank chamber was aerobic. The second stage in the whole system which is the epandage or soakaway is aerobic. In the tank itself apart from possibly a bit of activity in the crust the action is anaerobic. This is what you want as anareobes are much more efficient at reducing solids.

I agree that it's all a bit baffling if you don't have a background in biology. Once upon a time I worked for a company that did lab work for water companies and trying to get some of the finer points through to the engineers was an uphill struggle.

[Weedon]

[quote]First congratulations Motorhead you certainly appear to know your stuff or B******t baffles brainscan you advise me on some points1 The second stage of the tank the liquid stage aerobic (you say,) sh...[/quote]

We have exactly what you describe in our F/S, a plastic bucket with holes in it for which we were given a load of magma which should be taken out from time to time to be hosed down (near the tomatoes!).  If I were you I would get onto whoever supplied the tank and ask for them.

We have gone down the DIY chemin on lots but on the F/S front I was happy to start with the maire and pay others to do it for me whilst I supped the beer and took the pictures.

Incidently since we moved to France I have had many a good chin wag about fosse septiques but cannot once recall discussing my sewer in blighty.

weedon

[Motorhead]

Weedon's right, the French just are not as squeamish about these things.

[VJ]

Thank you all for the advice.

[Dave&Olive]

hi since I moved to France I do get little white spots in my stools , do you think I am eating to much fat???

        joke you know your stuff

              dave

ps they say never shake hands with a vet ( you never know where they have been) but with your knowledge of sceptic tanks think I will classyou as a vet