Tankless Water Heater Repair in Phoenix
The call this page is for is a tankless heater that has stopped behaving: a code on the display, a shower that swings from hot to cold, or a burner that clicks and will not light. What determines the repair is which of the three supplies has run short: gas to the burner, spark at the igniter, or a clear path for water through the heat exchanger.
American Discount Plumbing has repaired water heaters across the Valley since 2000. Owner Pavel Farcas (Paul) prefers Navien for new installs, services every brand, and backs tankless repairs with a one-year warranty. When he quotes a repair, he also tells you whether the heater is worth repairing at all.
AZ ROC Licensed #150707
Licensed, Bonded & Insured
All Tankless Brands Serviced
1-Year Repair Warranty
Same-Day Service Available
Family-Owned Since 2000
Error Codes Read Right
Scale and Ignition
Gas Line Know-How
Every Brand
1-Year Warranty
Pavel (Paul) Answers
AZ ROC Licensed #150707
Licensed, Bonded & Insured
All Tankless Brands Serviced
1-Year Repair Warranty
Same-Day Service Available
Family-Owned Since 2000
Error Codes Read Right
Scale and Ignition
Gas Line Know-How
Every Brand
1-Year Warranty
Pavel (Paul) Answers
Three Tankless Problems That Often Mean a Repair, Not a New Heater
Three complaints come up again and again. Each one sounds like the end of the heater, and each one is more often a part, a filter, or a gas line.
“My tankless is flashing an error code.”
The code is the first piece of information you have, and the manual explains what it means.
Tankless heaters report their own faults, and the owner's manual explains each code. Navien's manual lists E003 as ignition failure, with checking the gas supply as the first step. Rinnai's code 11 means no ignition, and its code 12 is flame failure, which its checks tie to the gas supply and the flame rod. Scale codes are a different page; our tankless descaling page owns those. Having the code and the model number when you call gives us a head start.
“My water goes cold in the middle of a shower.”
Scale lockout or a starved gas line: the Phoenix classic.
A heat exchanger lined with scale overheats, so the unit cuts the burner to protect itself and relights, and the water swings hot and cold. Gas is the other suspect: a supply line sized for an old tank may not keep up with a tankless burner at full fire. Descaling will not fix a gas problem, and a bigger gas line will not fix scale.
“It clicks, but it never lights.”
Gas supply first, then the igniter: the no-spark sequence.
Rinnai's steps for a no-ignition code start with the gas supply and the igniter, and a flame-failure code adds the flame rod, which can build up carbon. If the gas supply checks out, a worn igniter or a fouled flame rod is a parts repair.
Two more complaints, and what they point to
“Hot water takes much longer to reach the tap than it used to.”
A slow start is not always a fault.
A tankless heater starts from cold water sitting in the pipes every time, so the bathroom farthest away always waits. If the wait has grown, a clogged inlet filter or scale slowing the heat exchanger can add to it. If it has always been long, the fix is recirculation, as explained on our recirculation pump page, and no repair is needed.
“Why will it not go as hot as I set it?”
Check the setting before anything is taken apart.
Some models cap the temperature on purpose. Rinnai's tech sheet for its R75LSi and R94LSi lists a default maximum of 120°F. If the setting is right and the water still falls short, the inlet filter and the heat exchanger are the next places to look.
Tankless Problems We Repair
If you smell gas, skip both. Leave the house and call Southwest Gas at 877-860-6020, or 911, from outside.
Ignition and error codes
Temperature and flow
Leaks and drips
Two safe checks before you call
How a Tankless Repair Goes
You reach a person, not a phone tree
Call (602) 883-2787. Tell us what the display shows and what the water is doing.
We confirm the cause on site
The first checks are the gas supply, venting, filters, and scale.
You see the price before any work
The repair price is written down first.
We make the repair
Parts go in, the unit is fired, and the temperature and flow are checked at the tap.
We back it for a year
Tankless repairs carry a one-year warranty.
Serving Phoenix From Our Phoenix Base
American Discount Plumbing is based in Phoenix and serves all of Phoenix.
What Tankless Repair Costs in Phoenix
The price depends on which part failed, so we will provide a written quote once we have identified the cause. There is a $75 service fee if we come out and no work is done. If we do the repair, there is no service fee.
When repair is the right call, and when it isn't
Igniters, flame rods, sensors, fans, and condensate lines are repairs. A cracked or badly scaled heat exchanger on an older unit can be costly enough that a new heater is the better investment. When the two numbers are close, you see both side by side, and a new heater's installation is 10% off.
What We Typically Find on Tankless Calls
American Discount Plumbing vs. the big national chains
A unit that lights, runs a minute and drops out
The burner catches, the water warms, and then the heater quits and posts a flame-failure code.
Rinnai lists carbon on the flame rod among the checks for that code, and a gas line shared with a newer appliance can starve the burner once it is at full fire. We look at the rod and we look at what else is on the line.
A no-ignition code right after other gas work
A unit that stopped lighting soon after a new range or grill line went in.
The cause can be a valve left partly closed or a line now shared by more appliances than it was sized for. We can size and correct the gas line as part of the repair. Until then, ask whoever did the gas work to confirm the heater's valve was turned back on, and never reopen a gas valve you did not close.
Phoenix Conditions Behind Tankless Repairs
Hard water behind the scale codes
Phoenix water ranges from 10 to 17.6 grains per gallon in the city's 2025 report, and the upper end of that range is harder than Navien's and Rinnai's limits. That is why scale and overheating codes top the repair list here. Our tankless descaling page covers the numbers and the yearly flush in detail.
Outdoor units and a lost power supply
An outdoor unit's freeze protection works only while it has power. Rinnai rates its outdoor units down to -4°F on power, but its freeze protection does not protect the exposed piping and valves outside the cabinet, and Navien's warranty does not cover freeze damage. On an outdoor installation, the power supply and the pipe insulation get a look for that reason.
The Parts Behind These Repairs, and the Clue Each One Leaves
A clue is where the search starts, not a diagnosis. Two parts can leave the same clue.
What Decides a Tankless Repair
01 Whether the heat exchanger is still covered
Navien's standard residential warranty for the NPE-A2 heat exchanger is 15 years, with shorter coverage for other parts. Navien and Rinnai both exclude damage from scale and hard water, so a heat exchanger that failed from scale is a paid repair even on a young unit. We check what failed before you file a claim you are likely to lose.
02 Whether the cause will come back
A code that returns within weeks of a repair means the cause remains. When it comes to scale, a yearly descale in Phoenix water, a clean air intake filter on models that have one, and insulated outdoor piping are what break the cycle, and none of them cost much compared to a heat exchanger.
03 Whether you have the records a claim needs
Navien states that skipping regular maintenance can void its limited warranty. Keep the install paperwork, the model and serial number, and a record of each flush, so a future claim has what it needs.
Tankless Repair FAQs
Still have a question? Call Pavel (Paul) directly and get a straight answer, no phone tree.
Yes. We service Navien, Rinnai, Rheem, Noritz, Bosch, and every other brand, whoever put it in.
One year on our tankless repairs.
Restoring power and following the reset steps in your owner's manual is fine. Do not open the unit or adjust gas fittings. If the code returns, the cause is still there.
Usually not. Navien uses E760 as a flushing and service reminder, and Rinnai's LC codes report scale buildup. Both call for descaling, which our descaling page covers.
Tankless heaters need a minimum flow before the burner fires. Navien's ComfortFlow models add a small buffer tank and a pump to handle low flow. If it shuts off at normal flow, that points to a fault worth checking.
It can be, since the unit has gas and electrical parts. Turn off the unit's breaker, close the cold-water service valve if you can reach it without touching wet components, and call.
Same-day service is available, Monday through Saturday, 7 a.m. to 7 p.m. Call, and we will give you a time.
What Our Phoenix Customers Say
Our Google reviews are public, and they cover every kind of job we do, from water heaters to gas lines. The live feed below shows the current rating and the latest reviews.
Tankless Acting Up? Call American Discount Plumbing
Tell us what the display shows and what the water is doing. You get a diagnosis, a written price quote before any work, and a repair backed by a 1-year warranty.
We find the cause before we write a price, and we stand behind the repair for a year. That is the American Discount Plumbing difference.
Need Tankless Water Heater Repair in Phoenix? Call American Discount Plumbing
Tell us what the display shows and what the water is doing. You get a diagnosis, a written price quote before any work, and a repair backed by a 1-year warranty.
We find the cause before we write a price, and we stand behind the repair for a year. That is the American Discount Plumbing difference.
A real person answers, usually Pavel (Paul), with a fast callback and same-day help when it is urgent.
Request a Free Quote
No obligation. We will call you back fast.
Honest plumbing done right, across Phoenix and the Valley. That is the American Discount Plumbing difference.
