adding more rads to system

[young plum]

Just a quick question.
In college today we where told you cant add on pipework for new rads at certain parts of the pipework.
Teacher said 3 parts you cant add on to and these where called the 3 ts...Could anyone explain abit more to me where and where not your allowed to add rads on
thanks

 

[kevplumb]

3 tees

flow
return
the other one

pumped

gravity

one pipe

two pipe

 

[young plum]

Cheers
So this means you cant add on to any pipework within these 3 areas.
If i wanted to add on a rad do i just t into 1 of the rads allready in the house