Can anyone give advice re replacing single valve microbore system? If you are a heating engineer and were replacing the boiler to a combi and the radiators to an inlet and outlet (or valve at each end- not sure of the technical jargon here). would you also replace underfloor pipework to prevent future clogging or would you be confident that the exisitng copper microbore pipework would clean up with a power flush.Would very much appreciate advice before I spend alot of money and end up with the same problem .