Yuck !!!!

[L Austin France]

Just washed out the prefilter on our fosse.
What a smelly, sh!tty job.
Onwards & upwards.
Next the Bac degraiser.

[Antonia]

Don't!!!!
I'm supposed to be doing mine this week but they keep forecasting rain. When I moved to France I never thought I'd become so knowledgeable on waste plumbing.

[Blaze]

What is a pre filter ?? We never had to do anything with ours except get the main chamber pumped out every 5 years and hosed down.

[MAD87]

@Blaze Ditto

[Antonia]

I'm sure an expert will be along shortly with chapter and verse but basically the pre-filtre goes between the main tank and the filter bed. It is filled with a filter medium ( normally a type of Zeolite ) which traps microscopic solids ( and any larger floating ones ) and prevents them from passing into the filter bed. The type of fosse dictates how often the medium needs to be cleaned. Last time I looked all fosses were required to have them. Ours was an addon to an existing tank and needs to be cleaned out twice a year.

[L Austin France]

What is a pre filter ?? We never had to do anything with ours except get the main chamber pumped out every 5 years and hosed down.

It's a 'bucket' full of lava rock (pouzzalane) that sits in a chamber on the fosse outlet.
The bucket has holes in it so that waste water on the way out of the fosse on it's way to the filter bed in the garden passes through the lava rocks which attract grease & other small solids to stop them passing to & blocking the slotted drain pipes in the gravel bed filter.
Eventually the rocks can hold no more 'yuck' & need hosing down to wash 'em. This is done by lifting the bucket out by it's handle.
Easily done but a bit niffy.

[Blaze]

It sounds much more complicated than ours was. All the waste went into a chamber and the sludge settled on the bottom, forming a nice crust. The liquids overflowed into a second, larger chamber which was automatically pumped out into the pipes leading to the filter bed ('raised in our case) when the liquid reached a certain level. No lava rock or bucket, no smell, no maintenance. When it was inspected after 17 years, we got a gold star. During a general discussion, he told us that the additives were a waste of money as they aren't necessary (we didn't use them anyway).
When the crust reached nearly to the top of the first chamber, we'd get it emptied.

[Antonia]

Sounds like you had a micro station. Different animal.

[L Austin France]

It sounds much more complicated than ours was. All the waste went into a chamber and the sludge settled on the bottom, forming a nice crust. The liquids overflowed into a second, larger chamber which was automatically pumped out into the pipes leading to the filter bed ('raised in our case) when the liquid reached a certain level. No lava rock or bucket, no smell, no maintenance. When it was inspected after 17 years, we got a gold star. During a general discussion, he told us that the additives were a waste of money as they aren't necessary (we didn't use them anyway).
When the crust reached nearly to the top of the first chamber, we'd get it emptied.

Not at all complicated. The prefilter is there to stop the small paricles of grease etc contained in the liquid passing through to the distribution pipes in the filter bed & eventually 'bunging up' their slots.

[L Austin France]

Just washed out the prefilter on our fosse.
What a smelly, sh!tty job.
Onwards & upwards.
Next the Bac degraiser.

Bac degraiser cleaned out
Just got to hose out the distribution manhole containing the weirs which ensure even distibution to the 3 lines of filter beds & job finished.