How to add a T pipe in an existing 6" drainage UPVC line

Hi metro, If its 6 inches in the basement, i'm guessing its the main sewer pipe running dowm a row of houses and is joined to others, not something for a diy person, but if you wanna go, do it, I can see from your IP address you are oversea's and the stuff we have here will not be available, Lets start by asking, Is it underground pipe ( tan coloured ) or black/grey coloured,

hello metro, was this any help? can we do any more to help you, any feedback is much appreciated

here's something that might work, you say the main pipe is 6 inch, to save you cutting in a live sewer, use a hole saw to cut a 3 and half inch hole in the top of the 6 inch pipe , drill in the top because all the shit will be running at the bottom and uses one of these,
www.screwfix.com/p/mcalpine-macfit-mac-1-wc-straight-pan-connector-white-90-112mm/78806#_=p then 4 inch pipe will go from there,