Thank you for your replies. To clarify a few things
- I live in rural Luxembourg - there is only one kind of sewerage, no separate storm water drains.
- When I said municipal drains - I simply meant the local sewerage system
- I have checked with the local authorities - there is no issue with connecting the pump discharge directly to the sewers
I have attached four photographs
- The first one shows the drains from the house connected to the drain built by the builder. He legged it and I had to finish the job myself. Despite the two bends the system works perfectly. I have allowed for a "T" to enable me to connect the rainwater etc next.
- The drainage system is from a German outfit called Frankische. I have spoken with them and they tell me that the large orange tube can double up as a sump pit - if I find the right size of pump to put into it.
- The third photo is the drain/manhole built on the property by the builder. There is no cover yet - he legged it, as I explained. It is this drain that ended up being just a tad too high for water from the drainage system to flow under gravity into the drain and then into the sewerage.
- Finally, there is a slightly wider shot showing the garage entrance. The OptiDrain manhole is to the left and the drains out of the house are to the right. The drain/manhole built by the builder is in the foreground-right.
negative gradient problem I have is that of connecting the drainage system with the sewerage via the drain. The rainwater downspouts are buried superficially and only need to be guided correctly.
I hope this clarifies my questions. I would rate my DIY skills not too badly but in this particular instance I am a newbie.