Tankless Water Heaters
Endless Hot Water · Space-Saving Design · Long Service Life
Our Approach to Tankless Water Heaters
How a Tankless Water Heater Works
- Flow sensor — detects water flow and triggers ignition
- Burner — fires on demand, no standby tank
- Heat exchanger — heats the water as it passes through
- Hot water out — instantly, only when it's needed
- Compact — mounts on the wall, saves floor space
Tankless water heaters heat water on demand, providing endless hot water while saving space and energy. J&R Mechanical Services installs propane and natural gas tankless systems properly sized for your household needs.
A tankless water heater heats water only when you need it, eliminating the standby energy loss of keeping a full tank of water hot at all times. This can meaningfully reduce your water heating costs depending on your usage.
We install tankless units from trusted brands and ensure proper gas line sizing, venting, and water flow for optimal performance. Not every home is a good candidate for tankless — we evaluate your situation honestly and recommend the best option.
Tankless water heaters last significantly longer than tank models with proper maintenance. While the upfront cost is higher, the longer lifespan and energy savings make tankless a smart long-term investment for many homeowners.
Is a Tankless Water Heater Right for a Cold-Climate Home?
Here is an honest, climate-specific caveat many websites skip: tankless output depends on how much the unit must raise the incoming water temperature. Groundwater arrives very cold in winter, so a unit that delivers a high flow rate in a warm climate delivers noticeably less here. That does not make tankless a bad choice; it means the unit must be sized for a real winter temperature rise, not the number on the brochure. We calculate your real flow needs — how many showers and appliances run at once — against true winter inlet temperatures before recommending a model.
Gas and propane tankless units need correctly sized fuel lines and venting for reliable performance. This is exactly the kind of project where local experience beats a one-size-fits-all playbook written for milder climates.
What Maintenance Does a Tankless Water Heater Need?
The one non-negotiable is periodic descaling. Minerals in the water gradually coat the heat exchanger; left alone, scale chokes efficiency, triggers error codes, and can shorten the life of the very component that makes the unit worth buying. Most manufacturers recommend a descaling flush roughly once a year — more often with hard water — and many tie warranty coverage to it.
A descaling visit is quick: we circulate a cleaning solution through the heat exchanger, clean the inlet filter, and check venting, gas pressure, and error history. Kept up this way, a quality tankless unit routinely runs well past the lifespan of a tank model. We service all major tankless brands, not just the ones we install.
Efficiency Maine
Rebates & Guidance
- By the numbers
Tankless coil units are the least efficient option
Efficiency Maine identifies tankless coil water heaters (heated off a boiler) as the least efficient common water-heating option, while gas-fired tankless units give endless hot water but may need extra venting work.
Source: Efficiency Maine - Rebate
$1,150 off a heat pump water heater
Efficiency Maine offers a $1,150 instant discount at participating retailers (or a mail-in rebate) on a qualifying heat pump water heater.
Source: Efficiency Maine - Recommendation
Give a heat pump water heater the right space
A heat pump water heater needs a room with at least 6-foot ceilings and a condensate drain, and it works best in an unheated or semi-heated space - installing it in a warm living area reduces its efficiency.
Source: Efficiency Maine
Program details as of Sep 26, 2026. Rebate amounts and eligibility change; confirm current terms at efficiencymaine.com.
Tankless Water Heater Error Codes and Descaling Guide
A tankless water heater watches its own gas pressure, water flow, ignition, and heat exchanger temperature, and it shows a code the moment one of those readings is out of range. The code itself is only useful once you know which manufacturer and model line it came from — the same number can mean something completely different on two different brands, and sometimes on two model lines from the same brand. We always confirm the exact model before touching anything.
This guide covers five tankless brands installed in Maine homes: Navien, Rinnai, Noritz, Rheem, and Takagi. For two of them, Noritz and Takagi, the manufacturer publishes a homeowner-readable code list we could verify directly and reproduce below. For Navien, Rinnai, and Rheem, the manufacturers keep code interpretation inside the model-specific service manual or route it through a support line rather than a public list, so we describe what those brands do tell owners and how we look up the rest before we generalize.
Navien — NPE-A2 and NPE-S2 Condensing Series
Navien's NPE-A2 and NPE-S2 lines are condensing tankless units with a digital remote controller (or a display on the unit itself) that shows a numeric code when the unit locks out. Navien's own support page directs owners to the downloads section for their specific series rather than publishing a single cross-model code table, and its technical support line is staffed seven days a week for code-specific help. Because the code meanings live in that model-specific manual, we pull the manual for the exact NPE series and check the unit's error history rather than work from a generic list. Most Navien controllers also store the last several codes in memory, which is worth reading before a service call — it can show whether a code is a one-time event or a recurring pattern.
Rinnai — Residential Tankless Models
Rinnai is direct about this on its own FAQ page: error codes vary by product, and the company points owners to their unit's installation and operation manual or to Rinnai support to interpret a code and trace the root cause rather than publishing a universal chart. Rinnai's residential units display the code on the digital remote controller. As with Navien, we treat the code as a starting point and confirm it against the manual for that specific model before recommending a repair.
Noritz — NR83DVC, NR98DVC, and NR98SV
Noritz publishes a homeowner-facing knowledge base with plain-language explanations for its common codes. These apply to the direct-vent condensing and standard copper-heat-exchanger models most often installed in homes; check your unit's data plate for the exact model before assuming a code below applies.
| Code | What it means | What to do |
|---|---|---|
| 11 | Ignition failure — the unit called for heat but didn't detect a spark or flame. | Often a buildup issue on the ignition or flame-sensing rod. Gas supply problems are also a cause. Gas troubleshooting is a job for a professional. |
| 12 | Flame loss during operation, most common on direct-vent models. | Frequently a venting configuration issue or a gas pressure problem. Needs a professional check of venting and gas pressure at multiple firing rates. |
| 14 | The heat exchanger overheated enough that the one-time thermal fuse shut the unit down. Scale buildup from hard water is the most common cause. | This fuse cannot be reset — it must be replaced, and Noritz recommends replacing the heat exchanger at the same time. Add a softener or scale-inhibiting device afterward. |
| 20 | The high-limit switch tripped because outlet water reached roughly 176–205°F, usually from scale reducing heat transfer. | A single reset is normal, but repeated 20 codes without investigating the cause typically lead to a non-resettable 14. Schedule a descale and combustion check. |
| 29 | The condensing unit isn't draining its condensate properly. | Check for a condensate line that's undersized, unsloped, or frozen. The line must be plastic and at least 1/2 inch inside diameter. |
| 71 | A problem with the circuit board's ability to drive the gas valve or solenoids. | Often traced to a non-pure-sine-wave power source (some battery backups or solar inverters) or wiring damage. Needs an electrical check. |
| C1 | Scale buildup detected inside the heat exchanger (premix models). | Requires a professional descaling flush. Left alone, scale damage isn't covered under warranty. |
Rheem — IKONIC, RTGH, RTG-R, and ThermaForce
Rheem's current residential tankless lines include the IKONIC condensing series, the RTGH condensing indoor line, the non-condensing RTG-R series, and ThermaForce. Rheem markets these with what it calls a digital thermostat with a self-diagnostic program, but the company documents specific fault codes inside the owner's manual and service bulletins for each model rather than a single published chart. We match the installed model to its own bulletin before diagnosing a code rather than assume it matches a different Rheem line, since a code on one Rheem series can carry a different meaning on another.
Takagi — T-KJr2, T-K4, and T-D2
Takagi's non-condensing T-KJr2, T-K4, and T-D2 units (built by A.O. Smith Water Products Company) display a numeric code on the remote controller, or a flashing red LED on the computer board itself, depending on the model. Takagi's own troubleshooting guide lists these plainly for homeowners and installers.
| Code | What it means | What to do |
|---|---|---|
| 03 (T-KJr2/T-K4) or 031 (T-D2) | Incorrect dipswitch settings, often the gas-type switch. | Confirm dipswitch positions match the installed gas type and setup. A job for the installer. |
| 10 (T-KJr2/T-K4) or 101 (T-D2) | Abnormal combustion — commonly a blocked vent, backflow preventer installed backwards, or a scaled-up heat exchanger. | Clear venting obstructions first. If the unit has run for years without a softener, scale is a likely cause and points to a descaling visit. |
| 11 (T-KJr2/T-K4) or 111 (T-D2) | Ignition failure after three attempts. | Checks include gas supply, gas pressure, and the igniter. Gas work needs a licensed technician. |
| 12 (T-KJr2/T-K4) or 121 (T-D2) | Flame loss while the unit was running. | Often linked to venting or gas supply; needs a technician visit. |
| 31 (T-KJr2/T-K4) or 311 (T-D2) | Output thermistor fault. | Thermistor replacement, performed by a technician. |
| 32 (T-KJr2/T-K4) or 321 (T-D2) | Inlet thermistor fault. | Thermistor replacement, performed by a technician. |
| 39 (T-KJr2/T-K4) or 391 (T-D2) | Air-fuel ratio (flame sensor) rod failure. | Cleaning or replacing the rod, performed by a technician. |
| 51/55 (T-KJr2/T-K4) or 510 (T-D2) | Gas valve or solenoid valve abnormality. | Requires a technician inspection of the gas valve assembly. |
| 61 (T-KJr2/T-K4) or 611 (T-D2) | Fan motor abnormality. | Fan motor inspection or replacement by a technician. |
| 70 (T-KJr2/T-K4) or 701 (T-D2) | Computer board fault. | Board inspection or replacement by a technician. |
Takagi's own manual sets the line at 7 grains of hardness (about 70–140 ppm): above that, a water softener isn't optional. Without one, scale builds on the heat exchanger, and Takagi states heat-exchanger failure from hard-water scale is not covered under warranty.
Descaling Frequency by Water Hardness
How often a tankless unit needs descaling depends on how hard the water actually is, not a flat annual rule. Noritz publishes a residential treatment table tied to grains per gallon (gpg): soft water (0–1 gpg) and slightly hard water (1–3 gpg) need no scheduled flushing. Moderately hard water (3–7 gpg) and hard water (7–10 gpg) call for a water treatment device or a flush about once a year if no device is installed. Very hard and extremely hard water (above 10 gpg) call for a treatment device outright — the manufacturer stops recommending flushing alone as sufficient at that point.
Maine's private well water commonly runs hard, and hardness can shift by season and by well, so a unit on well water without a softener is worth checking annually regardless of a lab result from a few years back. J&R's tankless descaling service circulates a cleaning solution through the heat exchanger and flushes the system, matching the procedure in the manufacturers' own manuals.
| Hardness level | Hardness (gpg / mg-L) | Treatment device | Flush frequency |
|---|---|---|---|
| Soft | 0–1 gpg (0–17 mg/L) | None | None |
| Slightly hard | 1–3 gpg (17–51 mg/L) | None | None |
| Moderately hard | 3–7 gpg (51–120 mg/L) | Treatment device suggested | Once a year if no device installed |
| Hard | 7–10 gpg (120–171 mg/L) | Treatment device suggested | Once a year if no device installed |
| Very hard | 10–14 gpg (171–239 mg/L) | Treatment device required | Required |
| Extremely hard | Over 14 gpg (over 239 mg/L) | Treatment device required | Required |
When a Code Means Stop, Not Reset
Most lockout codes above are designed to reset once the underlying problem is fixed, and a single reset to see if a code clears is normal. Repeatedly power-cycling a unit that keeps returning the same ignition, flame, or gas-valve code is not — on several of the units above, doing that is exactly how a resettable fault turns into a non-resettable one. Writing down the code, when it happened, and what the household was doing at the time (running a shower, starting a dishwasher, extreme cold) gives a technician a real head start over a bare code number.
If you ever smell gas near the unit, don't investigate it yourself — leave the area, and call your gas utility or 911 from outside the home. If a carbon monoxide alarm sounds, get everyone out and call 911.
Sources: Takagi Non-Condensing Models Troubleshooting Guide (T-KJr2, T-K4, T-D2) · Noritz Knowledge Base — Error Code 11 · Noritz Knowledge Base — Error Code 12 · Noritz Knowledge Base — Error Code 14 · Noritz Knowledge Base — Error Code 20 · Noritz Knowledge Base — Error Code 29 · Noritz Knowledge Base — Error Code 71 · Noritz Knowledge Base — Error Code C1 (premix models) · Noritz Knowledge Base — Hard Water Treatment Guidelines · Rinnai Residential FAQ (error codes) · Navien Support · Rheem Residential Tankless Water Heaters
Brand names and logos are trademarks of their respective owners, shown only to identify the equipment discussed. J&R Mechanical Services is an independent contractor and is not affiliated with or endorsed by these manufacturers.
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J&R Mechanical Services is an independent contractor — not a national franchise. Our technicians are not commissioned salespeople. We do the work you called us for, do it right, and earn the next call.
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Tankless Water Heaters FAQs
Does a tankless water heater really provide endless hot water?
Yes, within its flow capacity. A properly sized unit will run a shower indefinitely without going cold. The limit is simultaneous use — run three showers and a dishwasher at once and you can exceed its flow rate. That is why honest sizing for your household matters more than the brand.
How long do tankless water heaters last?
Well beyond the life of a typical tank water heater, with annual descaling and basic care. The heat exchanger is the key component, and keeping it free of scale is what gets you the full lifespan.
Does cold groundwater affect tankless performance?
Yes, and it is the most important local factor. Winter inlet water in a cold climate can be dramatically colder than in southern states, which reduces a unit’s effective flow rate. We size for real winter conditions so your system performs in the coldest months, not just on paper.
Will you talk me out of tankless if it is wrong for my home?
Yes — and we do it regularly. We have no reason to push the more expensive option. If your usage, fuel situation, or budget points to a quality tank heater instead, that is exactly what we will recommend.
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