Surface drainage layout thoughts

[dangti6]

I have had an extension built over an existing soakaway and need to either reposition it or route the surface water to the front of the property as an alternative. At the front I believe the surface water goes to a drain rather than front soakaway.

 

My rear garden is not technically large enough to run a soakaway as in whichever direction I was to point, when 5m away from the building I am within 2.5 metres of the surrounding boundaries.

 

This rather lovely drawing visualises my thoughts, running around the garage extension to join up with the drainage at the front. 

 

 

I'd intend to fit roddable bottle gullies for the downpipes at the front and rear which would hopefully allow access to those sections between bends. 

 

The two 87.5 degree bends at the corners cause a run down the far right side which is inaccessible in the event of a blockage. Would a rodding point at one end of that long run suffice or do I need inspection chambers at each end?