Dodgy septic outlet?

A blocked outlet on my 15 year old septic led to my discovering the outlet pipe doesn't actually join to the main pipe leading to the garden trenches. It just butts down into a pipe coming sideways (up and out) out of the main pipe. Roots were causing the blockage. Is that dodgy plumbing or standard practice where the septic outlet joins the main pipe? As it has lasted 15 years I figure I could just wrap the dodgy connection in plastic and let it go at that.

Doesnt sound right, should be a glued fitting........