Valiant VCW242E Combi. HW and CH fine except sometimes no HW in loft and noticeable that water flow is not great (but HW always OK ground & 1st floor). House is NE London and quite high up. Thames Water said if can fill 1 gallon container in 30sec (1st outlet, street level) then pressure OK. Done test filling 1 gallon container, downstairs 20sec (cold), 30 sec (hot), but in loft 1 min (cold), 1min20sec (hot). At time of test unable to get hot water in loft, but CAN get HW in loft by leaving loft tap open and running HW downstairs and then shut downstairs tap - suggests that flow required (by boiler) to start delivering HW is greater than flow to keep it going.
Question - are there any settings on the boiler I can adjust to maximise HW flow - so HW pressure is closer to the CW pressure?
Question - are there any settings on the boiler I can adjust to maximise HW flow - so HW pressure is closer to the CW pressure?