Why do radiators on microbore systems have the feed and return at the same end?. Where we have double radiators they are f&r one end, the single radiators which have an internal pipe to circulate the hot water are also f&r from the same end - but we have some which have f&r in line. We are about to upgrade the entire system and replace the radiators and have read that microbore radiators should have f&r at the same end. Why? and does it matter if 'in line' radiators are fitted without a pipe to circulate the water?