There has been noise in the pipework between pump and boiler when water starts to heat for sometime and on return from a week break with CH off found boiler not working and clicking sound from diverter valve above pump adjacent to cylinder. Reset boiler which fired but did not heat water. Set timer to off and ticking persisted overnight. BGAS engineer called and changed pump but could not identify noise in pipework. He thought it might be debris moving in system and left quotation for Magnaclean. There are not other apparent faults in system.
I would be grateful if anyone can confirm his diagnosis or suggest other explanation for noise in pipes and whether Magnaclean would offer a solution. I quite like the idea of Magnaclean and have read good reports of it.
DIY explanation may not help as I am very inept at plumbing/electrics
With thanks in advance for responses