Before calling a plumber, a couple of quick checks will sometimes solve it. First, check the boiler is switched on at the fused spur and the pressure on the gauge is between roughly 1 and 1.5 bar — low pressure will shut a combi down and can stop the hot water. Second, check your programmer or smart thermostat is actually calling for hot water or heating. If you have a hot water cylinder, check the thermostat dial on the cylinder and — if there's an immersion heater — that it hasn't been left on accidentally. If none of that fixes it, phone us on 07784 066 853 and we'll talk it through before sending anyone out. Often a two-minute phone call saves a call-out charge.