Tankless symptoms: bursts of hot water, error codes, no heat
| What happens | Common cause | What the plumber checks |
|---|---|---|
| Hot water in bursts, then cold | Flow too low to trigger the heater, or scale restricting flow | Flow sensors, filters and the heat exchanger |
| Error code on the display | A specific sensor, vent, ignition or flow fault | The code in the unit's manual, then the part it names |
| Water never gets hot | No ignition or failed element, gas or power not reaching the unit | Gas supply, power supply, venting |
| Hot water fades over months | Scale building on the heat exchanger | Descaling and the condition of the inlet filter |
| Unit shuts off by itself | Overheat or venting problem | Exhaust path and temperature limits |
Write down the error code and what you were doing when it appeared. A code is the unit telling you which part of its system sees the fault, and it saves diagnostic time. If you smell gas, leave the house and call 911 and Southwest Gas at (928) 763-7467 before anything else.
Scale is the usual long-term problem
Tankless units heat water as it passes through a narrow heat exchanger, so mineral buildup there reduces flow and efficiency. Descaling, which flushes the exchanger with a mild acid solution, is the routine fix and is usually part of service. How often it is needed depends on the hardness of your water.
That figure is the missing piece for Bullhead City. The utility's published reports list sodium but not hardness, and the water comes from several groundwater systems that serve different parts of town. Call Bullhead City Utilities at (928) 763-9400 for the figure at your address, and check the manufacturer's maintenance schedule.
Should you flush, filter or soften
Descaling treats scale after it forms. A water softener treats it before the water reaches the heater, and a sediment filter at the inlet protects the unit from grit. Which of the three makes sense depends on how fast scale is forming and what the manufacturer's warranty requires. Read the manual first, since some warranties set maintenance conditions.
If you suspect scale is the main driver, the page on softener options explains what a softener does and what it adds. A softener adds sodium to the water, which matters for people on a low-sodium diet, and that is a question for a doctor and not for this site. Measure first, then decide.
Switching from a tank to tankless
What the house has to supply
A gas tankless unit usually needs a larger gas line than a tank heater and a dedicated vent. An electric unit needs a heavy electrical load, often more than a typical panel has spare. Both can be done, but the supporting work can cost as much as the heater itself, and it is worth getting quoted before choosing the unit.
What changes in daily use
A tankless heater does not run out of hot water, but it has a flow limit. Two showers and a dishwasher together can exceed what one unit delivers. Ask the plumber to size the unit to the household's peak use. Homes here range widely, and the median was built in 1991, so the layout may need changes.
The comparison with a tank is on the page for tank water heater replacement. Water heaters and gas piping are not on the city's permit-exempt list, so a tankless installation needs a permit. Ask who pulls it. The Building Division is at (928) 763-0124 for questions about your job.
Point-of-use and undersink units
Small tankless units mounted under a sink or near a remote fixture heat water where it is used, which shortens the wait for hot water in a far bathroom or kitchen. They suit one fixture and have a limited flow. They are plugged in or hardwired, so check the electrical supply nearby. A plumber can say whether one fits the fixture you have in mind.
Tankless water heater questions
Why do I get a burst of cold water in the middle of a shower?
Usually the flow dropped below what the unit needs to keep firing, or the heat exchanger is scaled. Check that the shower is not running too low and that other taps are not stealing flow. If it keeps happening, a plumber should descale and test the unit.
How often does a tankless heater need service?
Follow the manufacturer's schedule. It generally calls for periodic descaling, and more often where water carries a lot of minerals. Because the local hardness number is not published, ask the utility for it and let that number guide the interval between services.
Can a tankless heater use my existing gas line?
Sometimes, but many require a larger line than a tank heater. The plumber should check the line size, the length of the run and the other gas appliances sharing it before promising it will work, and should say whether a new line is needed.