No hot water at all
Upper element or upper thermostat on an electric unit, pilot or gas control on a gas unit. A tripped high limit also does this and it trips for a reason.
Some hot water faults are repairs and some are the tank telling you it is finished. A perforated tank cannot be fixed, and almost everything else can.
Water heaters give a fair amount of warning before they fail, and almost nobody acts on it. Noise from the base of the tank, water taking longer to recover, a relief valve that has started to weep, rusty water at a hot tap: each of those is a specific condition with a specific cause, and each appears months or years before the day a tank lets go.
The distinction that matters most is between a fault in the equipment attached to a tank and a failure of the tank itself. Thermostats, elements, gas valves, thermocouples, pilot assemblies, dip tubes and anodes are all serviceable parts. The steel vessel with a glass lining is not, and once it perforates the only answer is replacement.
Ignition sequence and flame condition on gas units, element resistance and thermostat operation on electric, incoming and outgoing temperature, evidence of sediment, anode condition where it is accessible, relief valve function and the system pressure that may be causing it to discharge.
Four checks that separate a serviceable fault from a failed vessel.
Start with whether the unit is producing heat at all. On an electric tank that means measuring the resistance of both elements and testing both thermostats, because a failed upper element produces no hot water while a failed lower element produces a small amount that runs out quickly. Those two symptoms are different and they point at different parts, which is why a technician who replaces both as a matter of course is not diagnosing.
On a gas unit it means watching the ignition sequence. A pilot that will not stay lit points at a thermocouple or a thermopile that has lost its output, at a draft problem disturbing the flame, or at a gas control that has failed. A burner that lights and then goes out shortly afterwards is usually a flue or combustion air issue rather than a fuel one.
Next comes sediment, which is the slow killer of tank water heaters. Mineral precipitates out of heated water and settles at the bottom of the vessel, where it insulates the steel from the water above it. On a gas unit that means the burner is heating sediment rather than water, which overheats the steel and produces the rumbling sound people describe as the tank boiling. On an electric unit it buries the lower element.
Finally the relief valve. A temperature and pressure relief valve that is discharging is almost never a faulty valve, and replacing it is the wrong response. It is reporting either an overheating condition or excessive system pressure, and system pressure is commonly the answer in buildings with a check valve or a pressure reducing valve on the incoming supply and no expansion tank to absorb thermal expansion.
Four conditions that end a tank, against a long list of faults that do not.
Six presentations and what each typically indicates.
Describing the pattern accurately matters here. No hot water at all is a different fault from hot water that runs out quickly, which is different again from hot water that is only lukewarm.
The water on the floor entry is the one that does not wait for a scheduled appointment.
Upper element or upper thermostat on an electric unit, pilot or gas control on a gas unit. A tripped high limit also does this and it trips for a reason.
Lower element failed, a broken dip tube mixing cold into the outlet, or sediment occupying a substantial share of the tank volume.
Water trapped under a sediment layer flashing to steam. On a gas unit this is also overheating the steel above the burner.
The glass lining has failed and the steel is corroding. If the anode has been depleted for years this is usually the beginning of the end.
Overheating or excess system pressure. Almost never the valve itself, and never something to cap or plug under any circumstances.
Could be a fitting, a relief discharge line or the vessel itself. If it is the vessel, the unit needs isolating and replacing rather than repairing.
Six steps from arrival to a working system or an honest replacement recommendation.
Where water is actively escaping, the first action is isolation rather than diagnosis. Getting the supply shut off and the discharge controlled comes before anyone works out why.
Cold supply isolated, unit powered down or gas shut off, and the immediate water problem controlled before any diagnosis begins.
Electric elements and thermostats measured, or gas ignition sequence observed and thermocouple output checked, depending on the unit.
Sediment, anode condition where accessible, evidence of corrosion at fittings and seams, and the age of the unit from its data plate.
Incoming pressure measured and the presence of an expansion tank confirmed, because that is what causes most relief valve discharge.
The fixed price for the repair given and approved before anything is fitted, or an honest replacement recommendation with the evidence.
Fault corrected, recovery time and outlet temperature checked, relief discharge routed correctly and the findings sheet left with you.
A very common fault with a cause that has nothing to do with the water heater and everything to do with the plumbing feeding it.
Water expands as it is heated. In an older plumbing system that expansion simply pushes back into the incoming main, which acts as an infinite reservoir, and nothing happens. Modern systems frequently have a check valve, a backflow preventer or a pressure reducing valve on the incoming supply, and any of those turns the building into a closed system where that expansion has nowhere to go.
The pressure then rises every time the water heater fires. It can climb well past normal supply pressure within a single heating cycle, and the first thing to give is the temperature and pressure relief valve, which opens to protect the tank. That is the valve doing exactly what it is for. Replacing it achieves nothing, and capping it is dangerous enough that it should never be considered.
The correct answer is a thermal expansion tank fitted on the cold supply to the water heater, sized for the system and pre charged to match the incoming pressure. It absorbs the expansion and the relief valve stops discharging. Where the incoming pressure is also high in its own right, a pressure reducing valve gets checked or fitted as well, because sustained high pressure shortens the life of everything in the building.
Repair against replacement, tankless, flushing, anodes and what the noises mean.
The dividing line is the vessel. If the steel tank itself has perforated or is seeping at a seam, it is replacement. If the fault is in a component attached to the tank, it is almost always worth repairing.
Age informs the decision without deciding it. A unit well past its expected life with heavy sediment and a depleted anode is a poor candidate for an expensive repair, and that gets laid out with the evidence rather than asserted.
On a unit that has been flushed regularly since installation, yes, and it is straightforward maintenance that meaningfully extends the life of the appliance.
On a tank that has never been flushed and has years of compacted sediment, it needs care. Disturbing a heavy sediment layer in an older tank can unseat debris onto a drain valve that then will not close, so it is assessed before it is attempted.
It is a sacrificial metal rod inside the tank that corrodes in place of the steel lining. It is the single component that determines how long a tank lasts, and it is the one nobody ever checks.
Replacing a depleted anode on a tank that is otherwise sound is inexpensive and can add years. On a unit where the anode has been gone for a long time and the water is already discoloured, it is too late and that gets said honestly.
It depends on the building and the usage. Tankless units deliver continuous hot water and take up less space, and they avoid standby losses. They also need a larger gas supply, different venting, and annual descaling in hard water areas.
The switch is a bigger job than swapping a tank, because the gas line, the venting and often the electrical supply all change. Where those are straightforward it can be a good decision, and where they are not the cost comparison shifts considerably.
It can, and it is worth understanding the trade off first. Higher storage temperatures increase scald risk at the tap, which matters in households with young children or older occupants, and they accelerate scale formation.
Where higher storage temperature is genuinely wanted, a thermostatic mixing valve on the outlet gives you the storage benefit without the scald risk at the fixtures. That is the safer arrangement and it is not expensive.
Shut the cold supply valve above the unit and turn off its power or gas, then call. Those two actions limit the damage far more than anything anyone can do on arrival.
If the leak is from the vessel rather than a fitting, the unit needs replacing rather than repairing, and it is worth knowing that before the visit so the right options can be discussed.
Diagnosis in Alamo, GA separates a serviceable fault from a finished tank, with the evidence either way.
Call with whether the unit is gas or electric, roughly how old it is, and what the symptom is: no hot water, not enough, discoloured, noisy or leaking. Those four descriptions point at different parts.
If a relief valve is discharging, mention it specifically. That usually means the plumbing feeding the unit needs attention rather than the unit itself.