I have been lucky to have owned 3 houses in my life and as fate would have it I have had issues with 2 hot water systems. I am not a technical person, so when hot water fails to come out of the tap, I leave it to the plumber that I have had for 10 years NJR Plumbing (located at Clontarf on Brisbane Northside). They have always been reliable and have had my hot water back on quickly. They have plenty of information on their website under hot water system repairs for anyone that is interested. I highly recommend them.