adding extra radiator

[DARREN]

hi can someone give me some advice i need to install an extra radiator in the lounge but cant get access to pipes under the floor can i tap off the existing living room rad which also supplys the hallway rad supply is 15mm pipe any help would be great

 

[petej]

You should be all-right doing this unless the radiators on these 15mm pipes are unusually large (high output) or you have a poor water flow through the system.
Do the existing rads on these pipes get hot enough in a reasonable time ?