That white crust forming around your faucet aerators isn’t just cosmetic. If you’ve noticed it getting worse or if the wait for hot water has been creeping longer month by month, your tankless water heater is telling you something specific. Unlike a traditional tank that sits full of water, a tankless unit fires on demand and pushes every gallon through a compact heat exchanger. That geometry is efficient, but it also means dissolved minerals have one concentrated spot to land. In Hurst, there are a lot of dissolved minerals to deal with.
Most homeowners here know hard water is “a DFW thing,” but the actual source matters more than the reputation. Where your water comes from and what’s in it changes how you should maintain your system and how you protect the warranty that came with it.
Why Hurst’s Water Is Rougher on a Tankless System
Hurst’s tap water is typically 95 to 98 percent purchased surface water from the City of Fort Worth, drawn from four reservoirs: Benbrook, Eagle Mountain, Cedar Creek, and Richland Chambers. The remaining supply comes from six city-owned wells drawing from the Trinity Aquifer, a formation beneath Tarrant County that naturally yields very hard water. By the time that blend reaches your water heater, Fort Worth and Dallas municipal water commonly tests in the 8 to 15 grains per gallon (gpg) range. Above 7 gpg is classified as hard, and above 10.5 gpg is very hard.
A tankless unit’s heat exchanger is where this becomes a problem. As water passes through and heats rapidly, dissolved calcium and magnesium carbonate drop out of solution and bond to the metal surface as calcium carbonate scale, commonly called limescale. Because a tankless system doesn’t store water, every gallon your household uses flows through that exchanger. Over time, the scale layer thickens, restricts flow, reduces heat transfer efficiency, and forces the unit to work harder to deliver the same output.
How Often DFW Homes Should Descale
Manufacturer maintenance schedules reflect local water conditions, and the guidance is more specific than most homeowners realize. Rheem’s published documentation sets a baseline descaling interval of at least once per year, shortening to roughly every six months in hard water service areas. At 8 to 15 gpg, Hurst sits well inside that threshold. Navien’s warranty terms are equally direct: improper maintenance, including failure to address scale buildup, is listed as a condition that voids coverage.
That last point has a practical implication beyond the maintenance itself. If you file a warranty claim on a failed heat exchanger, the manufacturer can request service records confirming the unit was maintained on the recommended schedule. A flush that isn’t documented is nearly as risky as one that never happened. Keeping records of who performed the service and when is as much a part of warranty protection as the descaling itself.
Signs Your Tankless Unit Needs Descaling Now
The most reliable early signal is a hot water delay that keeps getting longer. Some delay is normal for most tankless installations; a lengthening delay means the system is losing efficiency, and scale on the heat exchanger is the most common cause in hard water areas like Hurst.
These warning signs are also worth watching for:
- Error codes on Rinnai units: Rinnai displays an “LC” or “00” error code when internal sensors detect a lime or scale condition severe enough to require attention. If you’ve seen either of those codes, the unit isn’t prompting a general service visit. It’s specifically flagging scale.
- Fluctuating temperature mid-shower: Scale buildup disrupts consistent heat transfer, causing water temperature to swing unexpectedly.
- Reduced flow rate at the tap: Significant scale accumulation can restrict water flow through the heat exchanger itself, reducing output pressure.
- Unusual noises during operation: Popping, knocking, or hissing sounds while the unit fires are often caused by water forcing through narrow, partially blocked passages.
DIY Flush or Call a Plumber
A descaling flush involves isolating the unit using its service valves, connecting a recirculating pump and reservoir to the cold-in and hot-out ports, and circulating a cleaning solution through the system in a closed loop. For a unit on a routine annual schedule, that circulation typically runs about 45 minutes. For a unit that hasn’t been serviced in two or more years or one displaying error codes, the process can run up to two hours and may need to be repeated.
Where DIY descaling creates risk isn’t in the procedure itself but in the chemistry. Some homeowners use undiluted white vinegar, which is too acidic for extended contact with certain heat exchanger metals. Others mix cleaning products without checking compatibility. Either mistake can corrode components that aren’t covered under warranty once chemical damage is identified as the cause. A vinegar flush also won’t tell you anything about your combustion venting, inline filter screen, burner, igniter, or sensors. Rheem’s own guidance recommends that tasks involving gas lines, burners, or electrical components be handled by a licensed professional. A professional visit covers the flush and a full system inspection, which is where problems that won’t show up on an error code get caught before they become expensive.
For homeowners considering a water softener or whole-house inline softening system, it’s a reasonable long-term investment given Hurst’s hardness range. It lengthens the time between service visits, but it doesn’t eliminate the need for them or replace a professional inspection of the full system.
Staying Ahead of Scale in Hurst
A tankless water heater installed in a Hurst home is working against 8 to 15 gpg water from the day it starts up. Staying on a locally appropriate schedule, roughly every six months given the Fort Worth-sourced supply, protects both the unit’s lifespan and the manufacturer warranty behind it.
If your unit is displaying error codes, your hot water wait has been getting longer, or you’re simply not sure when it was last serviced, C&E Pipe Services can take a look. We’ll tell you exactly what your system needs and nothing extra. Reach us at (682) 297-4090.