The hot water went cold or lukewarm. Where do I start?
Start by noticing the pattern, because it points to the cause. A unit that gives no heat at all behaves differently from one that gives warm water that fades, or one that works at the kitchen sink but not the shower.
Ask three quick questions. Does it fail at every tap or just one? Does the display show a number or a letter code? Did anything change in the last day, such as a power flicker or a work crew on the street? Write the answers down, because they help whoever diagnoses it.
Checks a homeowner can do safely
These steps need no tools and no opening of panels. Stop the moment anything smells like gas.
- Look at the display. Write down any error code and find it in the manual, which usually lists a meaning.
- Check the breaker for the unit and for any nearby outlet. Flip a tripped breaker off and on once. If it trips again, stop.
- Confirm the gas shutoff on a gas model is in the open position, with the handle in line with the pipe. Do not relight pilots on parts you do not know.
- Check that the hot and cold isolation valves at the bottom are fully open.
- Run the hot tap at a steady medium flow. Tankless units need a minimum flow to fire, so a barely open tap can stay cold.
- Try a second hot tap. If one tap is cold and the other is hot, the problem may be a faucet cartridge, not the heater.
What Dania Beach Homeowners Should Know About Water and Gas Supply
Dania Beach runs its own water system, and low pressure from the city side can look like a heater fault. On February 18, 2026, a water main break near SW 54th Street and 40th Avenue put 41 residents under a boil advisory, according to WSVN. If every tap in the house is weak at the same time, ask neighbors and check the city's notices before blaming the heater.
The city's 2024 water quality report says the water is softened with lime and nanofiltration and disinfected with chlorine. It does not publish a hardness number, so we cannot say how fast scale forms in your unit. Follow the flushing interval in your manual.
Peoples Gas lists Dania and Dania Beach among the Broward communities it serves. If you smell gas, leave, call 911, then call the gas company printed on your bill. For homes in Davie or West Park, the same safety steps apply.
- Peoples Gas tariff service list
- City of Dania Beach 2024 water quality report
- WSVN news report (February 2026 main break)
- PHMSA gas leak guidance
Why a tankless heater runs cold when two taps are open
The heater has a maximum flow it can heat. DOE says demand-type units typically deliver about 2 to 5 gallons per minute. If a shower and a dishwasher both draw hot water, the unit may reach its limit and the temperature drops at both.
Turn one tap off and wait 30 seconds. If the water warms up, the heater is working but undersized for your peak use. That is a sizing problem, not a failure, and the answer may be a larger unit or a second one.
Hard water and scale can stop a tankless heater from firing
Family Handyman notes that mineral buildup can keep a tankless unit from switching on, and that tank heaters need yearly flushing. Scale coats the heat exchanger and narrows small passages, and the unit may throw a code or shut down to protect itself.
Flushing a tankless unit means connecting hoses to service valves and circulating a descaling solution, as your manual directs. Some owners do this themselves. If you have never done it, or the valves are stuck, we would rather you call than force a fitting and cause a leak.
When to stop and call a plumber
Some problems are not safe to chase on your own. Call if any of these appear:
- You smell gas. Leave the house, call 911 from outside, then call your gas utility.
- The display shows an ignition, flame or exhaust error that returns after one reset.
- You see water leaking from the unit or the vent.
- There is soot, discoloration or a burning smell around the unit.
- The breaker keeps tripping.
- Water is only lukewarm even after you have checked flow and valves.
What to have ready before you call us
A good description saves time. Tell us the brand and the rough age from the rating label, whether the unit burns gas or uses electricity, and the exact error code on the display.
Say what you have already tried, such as one breaker reset or a check of the isolation valves. If water is leaking, shut the cold supply valve to the unit first and tell us.
We cannot diagnose a burner or a heat exchanger over the phone, and we will say so. What we can do is tell you whether the symptoms sound like a sizing issue, a scale issue or a failed part, then send a plumber with a plan. When you are ready, Call (954) 697-4920.
A quick symptom guide
Use this table to match what you see with the most likely cause and who should handle it.
| Symptom | Possible cause | Who handles it |
|---|---|---|
| Display blank, no heat | No power, tripped breaker | Homeowner may reset breaker once |
| Burner clicks but never lights | Gas supply or ignition fault | Plumber |
| Hot at first, then cold | Flow too high, scale, or sensor issue | Homeowner checks flow, plumber for the rest |
| Weak flow at every tap | Clogged inlet filter, closed valve, low supply pressure | Homeowner checks valves, plumber if still weak |
| One tap only is lukewarm | Faucet cartridge or mixing valve | Plumber |
| Error code repeats | Varies by model | Plumber, with the code written down |
Frequently Asked Questions
Can a water main break or boil water notice stop my tankless heater from heating in Dania Beach?
It can. Low flow or pressure from the street can keep the flow sensor from firing the unit, and sediment can come loose after work on a main. Check the city's notices, clean the inlet filter if your manual allows it, and call us if flow stays weak.
Is it safe to reset my tankless water heater?
A single reset by breaker or the power button is generally fine for most models. Do not reset repeatedly. If a code returns, there is a cause that needs a plumber.
Why does my tankless heater give hot water for a minute then go cold?
Common causes are too much demand, scale on the heat exchanger or a flame sensor problem. We cannot tell which by phone, but the error code helps.
Should I drain a tankless heater myself?
Descaling is a maintenance task that some owners do with the manufacturer's instructions. Do not open sealed panels, touch gas parts or force stuck valves.
Do you repair tankless units at night?
Our line is open 24/7 for emergency dispatch. Call (954) 697-4920 and read the error code to us. For a unit that is past repair, see our tankless water heater service or water heater repair.
Code reference: plumbing work in Florida falls under the Florida Building Code, Plumbing (8th Edition, 2023), which is based on the 2021 International Plumbing Code (IPC). Ask the Dania Beach Building Division whether your job needs a permit.