Plastic Central Heating Leak Underfloor and Changing for Smaller Size Pipe All aspects of plumbing questions and answers, help, tips and information

[Dieseldic]

Hi, under our kitchen floor there’s a 22mm polypipe central heating flow and return which has a leak somewhere. Someone told me you can have a smaller pipe installed inside instead the old pipe instead of digging the floor up. Is this possible? Would the central heating still function with a smaller pipe up the middle?
Any help would be much appreciated
Richard