cold rad

[joe22rm]

i just moved into a 1930s house and have a problem with a cold radiator i cant solve..
the radiator is in a conservatory which is onto an extension, the supply pipe is 15mm and t\\\'s off into two 8mm microbore one to extension 2m and one to conservatory 6m.
the radiator in the conseratory has good hot supply but when the lockshield valve is opend it is flooded with cold water from cold return. it seems the cold return from the radiator is of higher \\\\or equal pressure than the feed
is there anything i can do or is this down to bad design.

 

[Nige F]

Microbore can you get at it and replace with 15mm.

 

[joe22rm]

i can get to the pipe and replace with 15mm.
do you think this will solve my problem of having more water pressure from the return side.
should i replace the other side of the t (to good rad in kitchen)also?
thanx joe