For Electric Water Heaters
Check the Breaker First
This is genuinely the single most common cause of a complete hot water loss on an electric unit — a tripped breaker cuts power entirely, and it's often not obvious from looking at the panel unless you check specifically. Locate your electrical panel, find the breaker labeled for the water heater (or test by process of elimination if it's unlabeled), and check whether it's in the tripped (middle) position rather than fully on.
If the Breaker Is Fine: Heating Element or Thermostat
Electric tank water heaters typically have two heating elements — upper and lower — each controlled by its own thermostat. If the upper element or thermostat fails, you may lose hot water entirely even though the lower element could theoretically still work, depending on the specific wiring configuration. This level of diagnosis typically requires a multimeter and some electrical knowledge, making it a reasonable point to call a plumber or electrician rather than continuing to troubleshoot independently.
For Gas Water Heaters
Check the Pilot Light
Most standard gas water heaters have a viewing window near the bottom where you can visually confirm whether the pilot light is lit. If it's out, most units include instructions directly on the tank for relighting it — this is often a straightforward homeowner task if you're comfortable following the printed steps carefully.
If the Pilot Won't Stay Lit
A pilot that relights but goes out again shortly after, repeatedly, usually points to a failing thermocouple — a safety sensor that detects the pilot flame and, if it can't reliably sense it, shuts off gas flow as a safety measure. This is a common, relatively inexpensive part to replace, and not something to keep manually relighting repeatedly without addressing the underlying cause.
If There's No Gas Smell and the Pilot Won't Light at All
This can indicate a gas supply issue upstream of the water heater, or occasionally a faulty gas control valve — worth calling a plumber rather than continuing to attempt relighting if the pilot won't catch at all despite following the instructions correctly.
For Tankless Water Heaters
Tankless units typically include a digital display that shows an error code when something's wrong, which is genuinely useful for diagnosis compared to a tank unit's more limited troubleshooting options.
Common Error Code Categories
A code related to cold weather shutoff can appear if outdoor temperatures dropped low enough to trigger the unit's freeze protection, particularly relevant during Arlington's occasional hard freezes for units with any outdoor-exposed components. An ignition failure code points to a problem lighting the burner, similar in nature to a pilot light issue on a tank unit. A flow-related error can indicate a clogged inlet filter or scale buildup restricting water flow through the unit — this is exactly the kind of issue regular descaling maintenance is meant to prevent.
What to Do With an Error Code
Note the specific code before calling — most manufacturers' documentation (often available via a quick search of the model number) explains what each code means, and having this information ready when you call helps a plumber arrive prepared with the likely-needed part rather than diagnosing from scratch on-site.
A Few Things Worth Checking Regardless of Water Heater Type
Confirm the issue is actually a complete loss of hot water, not just reduced temperature — these point to different causes, with reduced-but-present hot water often pointing toward a partially failed element or a thermostat set incorrectly rather than a complete system failure. Check whether other household members have also lost hot water, or if it's isolated to one fixture, since a single-fixture issue points toward a local problem (a failed mixing valve, for instance) rather than the water heater itself.
When to Stop Troubleshooting and Call
If you smell gas at any point during this process, stop immediately and follow standard gas leak safety steps rather than continuing to troubleshoot the water heater. If the breaker and basic checks don't resolve an electric unit's issue, or if a gas unit's pilot won't reliably stay lit after a reasonable relighting attempt, these point toward component failures that need professional diagnosis and repair rather than continued DIY troubleshooting.
Need a Plumber in Arlington?
Licensed, upfront, and available 24/7. Call (571) 202-6461 or request a free quote.
Frequently Asked Questions
Is it safe to relight a gas pilot myself?
Most units have clear instructions printed directly on the tank for relighting — if it won't stay lit after a couple of careful attempts, that points to a part needing replacement rather than user error.
How long does a typical water heater repair take once diagnosed?
Most element, thermocouple, or valve repairs are completed same-visit, usually within an hour or two once the actual cause is identified.
Could a plumbing issue elsewhere in the house cause a total loss of hot water?
It's less common but possible — a failed mixing valve or an issue with the cold water supply feeding the unit can occasionally present as a hot water loss; a plumber can rule this out during diagnosis.
Why does my tankless water heater show an error code but tank units don't have this feature?
Tankless units have more electronic components managing the on-demand heating process, which allows for more specific diagnostic feedback than a simpler tank system typically provides.
Should I try replacing a heating element myself on an electric water heater?
This involves working with electrical components connected to a tank full of water — most homeowners are better served having this handled professionally given the safety considerations involved.
Is a sudden, complete loss of hot water ever an emergency?
Not typically dangerous on its own, though it's worth prompt attention especially in cold weather or for households with specific needs — call to describe your situation and we can advise on appropriate urgency.