What your system is doing, and what it usually means
No hot water at all. On electric storage this is most often a failed element, a tripped safety switch or a thermostat that has stopped calling for heat. On gas it is usually ignition: a pilot that will not stay lit, or a fault in the gas control valve. On heat pump and solar it can be the booster, the circulation pump or the controller.
Not hot enough, or running out sooner than it used to. On a twin-element electric tank, one element can fail while the other keeps working, which roughly halves your hot water. It can also be a thermostat drifting, a leak on the hot line quietly drawing the tank down, or a system that was always slightly small for the household and has finally been noticed.
Temperature that moves around while you are using it. On continuous flow this usually means demand is exceeding what the unit can deliver, so a second outlet opening drops the temperature at the first. On storage it more often points at a tempering valve.
Water where it should not be. A drip from the relief valve during heating is normal and by design. Water from the tank body, or a rust stain running down the casing, is not, and generally means the cylinder has corroded through.
Tripping the power. Almost always a failed element letting water reach the live part, with the safety switch doing exactly its job. Repeatedly resetting the switch is not a fix and is not safe.
Noise, discoloured water, or an error code on the controller. Noise is often sediment in the base of a tank. Discolouration can be corrosion inside the cylinder. Error codes are manufacturer-specific and worth sending us before we come out, because some point at a reset and others at a part.



