No Hot Water? What to Check First

By the Denver Urgent Plumber team · Updated September 2026

Confirm It Is Really the Water Heater

Start with the obvious question: is every hot tap cold, or just one? If a single shower runs cold but the kitchen sink is fine, the problem is almost certainly that fixture, usually a failing mixing cartridge or an anti-scald setting that has drifted. If the whole house has no hot water, the heater or its power or gas supply is the place to look. If the hot water is there but runs out in a few minutes, the tank is probably heating but not holding, which points at sediment, a failed lower element or a dip tube. Those three answers lead to three completely different visits.

Electric Units: Breaker, Elements, Thermostats

On an electric water heater, check the breaker panel first. A tripped double-pole breaker for the heater is a common and simple find, though a breaker that trips again immediately is telling you something is wrong and should not be reset a third time. Beyond that, the likely parts are the upper or lower heating element and the thermostat that controls it, plus a high-limit switch that cuts power when the tank overheats. A tripped high limit often means a thermostat has stuck, so replacing the switch without diagnosing the cause just buys a week or two.

Gas Units: Pilot, Thermocouple, Gas Valve

On a gas heater, look at the pilot. If it has gone out and the unit has printed relighting instructions, and you cannot smell gas anywhere near it, following those instructions is reasonable. If it lights and then dies within a minute, the thermocouple or flame sensor is the usual suspect. If it will not light at all, or it keeps going out after replacement, the gas control valve may have failed. One rule overrides all of this: if you smell gas, leave the house, leave the door open and call the gas utility from outside before you call anyone else.

Sediment, Rumbling and a Shorter Shower

A tank that pops or rumbles while it heats has sediment sitting on the bottom. On a gas unit that layer insulates the burner from the water, which makes the heater work harder and shortens the usable hot water. Draining the sediment out can restore a fair amount of capacity on a tank that is otherwise in good shape. It is worth asking about before anyone talks about replacing the unit, particularly if the heater is not yet at the end of its expected life.

Altitude Changes the Appliance

Here is something specific to living a mile up. Gas appliances burn differently in thinner air, so a water heater or furnace installed in Denver has to be rated or adjusted for high-altitude combustion. A unit that was swapped in quickly without that consideration can run poorly, short-cycle or produce complaints that have nothing to do with the tank at all. If yours was replaced by someone who was not local, it is a fair question to raise at the next service visit, and it is worth confirming before a new gas unit is ordered.

Water on the Floor Is a Different Question

If there is water around the base of the heater, the priority changes. It may be coming from a fitting, the drain valve at the bottom or the temperature and pressure relief line, and all three of those are repairs. If it is weeping from the tank shell itself, the heater is finished, because there is no repair for a rusted-through tank. Since most Denver water heaters sit in a basement utility room, a slow tank leak can run into a floor drain unnoticed for weeks. Check under and behind the unit, not just in front of it.

When to Stop and Call

Stop if you smell gas, if a breaker trips repeatedly, if the relief valve is discharging, if there is water you cannot account for, or if the unit is making noises you have not heard before. Those are not wait-and-see situations. It is also worth calling if hot water has been getting steadily worse over months rather than failing suddenly, because a gradual decline usually has a cause that a straight part swap will not address.

Arrange an Inspection

Denver Urgent Plumber tests the unit before condemning it. See what a visit covers on the water heater repair page, and if the tank is genuinely at the end of its life, the repair versus replacement guide sets out the questions to ask. Calls from newer homes with basement utility rooms, such as those in Centennial, often involve a pressure regulator as well. Describe what your heater is doing and we will bring the right parts.