Thanks for the replies, as suggested I'm going to ask some more questions of the vendor.
The Septic tank is registered with SEPA, as I understand it, it is the point of discharge from the tank within the garden that is registered with SEPA.
Its very unlikely that any new soakaway system could be implemented within the garden, as the garden is very small.
The deeds say I have a servitude right to a tail pipe, but on asking where this tail pipe was the Vendors are saying its the 2m pipe in the garden.
As Gus identifies, the fact that the tailpipe/soakaway ends exactly by the garden fence, not extending into neighbours land and not extending further towards the stream could be suspicious/problematic.
Given that the septic tank discharge is registered with SEPA, and the drainage arrangement is existing and historical, is discharge close to a water (or into) a water course allowable?
When the tank was registered, would the owner have to have declared the location of the discharge adjacent to the stream?
I.E does the fact that the tank is registered with SEPA mean that SEPA are aware how and where the discharge from the tank works, and are OK with this?
Thanks