I can't make now longer video because I have to met again the same problem with a same boiler. I can give you a bit longer description to can replace step by step. 1 Isolate Flow and Return (black leavers on video) 2 Drain the system by openinf drain valve located in the boiler (white drain valve) 3 Remove the nut from PRV 4 Remove the screw which is holding the PRV (with an Allan key) 5 Pull out the PRV Now you have to do the same tings in reverse order and by the end you have to fill up the system and test it. Don't forget to follow the manufacturer instructions. Page 54. mediacdn.baxi.co.uk/-/media/websites/baxiuk/files/product-literature/baxi-megaflo-system/baxi_megaflo_system_installation_and_service_manual.pdf?v=1&d=20230824T154719Z

@@bheating thankyou so much 👍