Hello,
so that our fosse can conform, we need to:-
Mettre un coude plongeant en sortie de bac à graisse. (Put a plunging elbow at the grease trap outlet?)
I am struggling to find out exactly what this is. Could anyone with knowledge please post a link to an image?
Thanks very much
Graeme
This diagram might help
From an earlier thread
Hang on - didn’t you start that thread?
In this context
Coude = bend
Plongant = descending
Yes. So?
I am sorry if contributors feel I am repeating topics, but I am afraid that nothing in previous threads have helped me to understand what a plunging elbow is.
So it would probably have been better to continue on that thread. No big deal though.
Fair enough - but it just seems to be a normal “coude” which takes the inflow pipe below the level of any floating grease in the trap.
The pipes are meant to be below the crud on the surface not pouring on top. Thus the elbow takes the flow down below the crud layer. It works without but not as well and it will smell a bit without.
since you were shown/told what the plunging elbow is… on the previous thread…
have you actually discussed this with your local plumbing merchant and/or professional plumbers… or anyone ???
If your outflow pipe is blocked, the water in the tank will rise… and could overflow through the tampon de visite and backup through the pipes to the house…
Pongy, one presumes 
actually happened to a neighbour, when new sewage drains were laid the wrong way from the house… water didn’t flow away, it just filled up the pipe and finally flooded the indoor toilet… and pongy was not sufficiently strong a word… it was a ghastly mess.
Thankfully OH came to the rescue (with large peg on nose, waders and elbow length rubber gloves…)… and, using spade to good advantage, dug down to find outside connection… disconnected it and reconnected at a lower lever to let “le stuff” flow…
poor chap got the worst of it when he had to actually break the pipe and the pressure was allowed to escape… all over him.
Or to put it in the words of Blaster Bate “A shower of shit over wherever” and am sure it wasnt in Cheshire.
Hello @Stella
I have been through my original thread and can find no clear explanation of what a plunging elbow is. In fact there are several variants of positions on inflow and outflow, of the fosse and the grease trap. Hence my asking a specific question again.
@JaneJones and others nailed it for me. This is a pipe I need to add in the grease trap where domestic water waste is discharged pre going into the fosse. Its not a big job thankfully.
Is it easy to find a plumber having just moved into a french house? It think not. In all my previous house renovations in the UK I have always done my best to understand what I am talking about before I talk with a tradesman. The proposition of finding a plumber, describing a problem that I did not understand, in french, was not something I was prepared to do.
The tone of your response indicates that somehow I have hit a nerve? I am really sorry if that is the case. All I was seeking was clear information. My apologies.
In your position I’d have tagged a post on the end of the old thread saying eg “sorry everybody, still not sure exactly what I need”.
As I said, no great problem that a new thread was started but I got slightly confused when you didn’t even mention the older conversation.
Certainly not hit any nerves with me… I was wondering (as I said) if you’ve made any progress discussing (and possibly showing the responses) to professionals.
There are many DIY stores within France and if you prepare your wording and take a good look around… you might well find what you are seeking and/or find someone who can talk you through things.
For me, the diagram says it all… re the elbow… but obviously not to you…
such is life… we all see things differently and elbows are just one of those things. 
cheers
Your best bet is the precious owners or your neighbours….we were lucky enough to “inherit” tradespeople with the house. Which is great as they know their way around the weird installation that precious owner put in.