Is the branch blanked off?
Do you mean the straight bit that comes to an end in the hole? If so - yes. But it is blanked off inside the pipe with a blanking plate set at an angle, like this:
As I can't see it. If so remove the blanking plug and get someone to feed your rods up the manhole and put your hand up the branch and 'push' the rod over into the drain line.
Great idea - I think....! How would I remove the blank though? And how can I ensure I would be able to get it back on again (and get it back on with a water tight seal?)
As to the question of what is blocked. Seems a bit complicated to me but here's where my understanding is through experimenting, asking the neighbours and getting some advice from my brother-in-laws dad (who works with septic tanks for a living)......
A crude drawing and most definitely not to scale. But should give an idea....
The bathroom and WC both drain to the septic tank and soakaway in the front garden.
***Apparently***, the kitchen sink and washing machine used to go there too, hence the pipe going back up to the main house from the inspection cover. The neighbour reckons that the woman who used to live here was worried about overloading the tank (and possibly other things to do with the tank too). A ditch was therefore created at the bottom of the garden to act as a soakaway, and the kitchen sink/washing machine now drain there - or at least are supposed to.... Who knows!!! And I'm guessing they are supposed to go there via the bend in the pipe which I was originally posting about. And that there is a block in there somewhere.... The neighbour says that the ditch used to sometimes fill a bit, but we've never experienced that in a year and a half of being here (we are low water users though and there are just two of us). BTW - it's more of a slope with a bit of gravel than an actual ditch....
So....
If I run my kitchen tap for a fair while, the water starts to get higher and higher in the inspection hole. After quite a while the water works its way though to the septic tank in the front garden. Hence the confusion! I am only assuming at the moment, but I think that when/if it was changed, they did not block the original route to the septic tank and the water can still therefore reach that area.
Thanks a million for the help.
Max.