Not a Fosse Septique?!

[Lyndzena]

Hello

Please can somebody help us identify our waste system.  When we bought our house in Calvados (Dec 04), the previous owners were adament that it wasn't a fosse septique, but was a biological wastage system.  They indicated that there wasn't a 'tank' as such.  With regards to maintenance they just said not to put any bleech or coffee grinds down the sink / toilet and that there was nothing to empty.  They said that Ariel, Persil, sun were all fine to use.

Since then, we have had sewage water back up into the cloakroom sink and washing machine hose after doing a weekends washing.  We have opened up a hatch in the floor of the back kitchen.  Underneath is a 'mini tank' which is about 2.5 foot by 1.5 foot and has all the waste water (some pipes are diverted into the house just to go through this mini tank) leading into one side from a pipe about 10cm in diameter.  This leads into one side on the mini tank, where there is soil and worms! (And what looks like loads of tissue paper).  There is then a concrete divide where the water seeps through the the other side and the pipe that leads out to under the garden (we presume).  The mini tank smells awful - which indicates to us that it is some sort of filter / initial filter / the biological waste system.

Before we found this hatch, we had a plumber round, who wanted to dig up our conservatory because he thought that the back up of sewage might be due to a brocken pipe - digging up my conservatory was not an option i liked, hence the investigations we did into the hatch (which looked like it hadn't been opened in years).  Anyway this doesn't give me much confidence that the plumber knows much about this system we have. 

Does anybody know what kind of system this could be?  I have searched the forum under fosse and got the impression that the Marie will have the original system plans etc - so that is one avenue we can explore.   If you do know what system it is, can you give me any info on it's maintenance?  From reading the forum - it also seems that we may need to have a fosse septique installed anyway to meet some regulations.  If so does anybody know what a fosse septique costs for a system supporting 4 bedrooms and 1 lounge/diner?  Also how long does it take to put one in?  (We have lots of sloping land, so could position down the land away from the house with a natural fall).

Thank you in advance for your help / answers / advice.

Lyndzena