Noritz doesn’t print a fixed calendar interval. Instead, its EZ owner’s guide says periodic flushing in hard-water areas is necessary, and an optional service reminder, code C1#, can tell you when the heat exchanger needs it. The guide sets a hardness limit of 12 gpg and says water above it should be treated to keep full warranty coverage. In much of the Wasatch Front, that points to regular flushing plus some form of water treatment.
Three warranty lines worth reading twice
Noritz is more specific about scale than most brands. Its EZ owner’s guide (for the EZ111DV and EZ98DV) has three separate lines that touch on it.
- Scale itself. The guide says problems resulting from scale formation are not covered. If the heat exchanger fails because of mineral build-up, the repair is yours.
- Hard water. The warranty terms state that hardness above 12 grains per gallon voids coverage for resulting damage. That ties coverage to a number you can look up in your city’s water report.
- Ignored reminders. The guide says damage after an ignored C1# flush reminder is not covered. If C1# appears, the clock is running.
Put together, a Noritz on untreated Utah water with no flush history is at risk of losing coverage on its most expensive part. Our warranty and scale guide explains how to keep records that hold up.
Noritz’s limit and local water
Noritz’s threshold is 12 gpg. Here is how some Salt Lake Valley and Utah County water compares.
Herriman is a good example of why the number matters. The city says the Jordan Valley Water Conservancy District (JVWCD) water it buys measures 12–15 gpg, while JVWCD’s own site says its water can range from 1–12 gpg. The two ranges only meet at their edges. Herriman’s own wells are harder still, at 25–60 gpg. A Noritz there could be over the line depending on which water reaches the house.
Riverton buys all of its water from JVWCD, so its figure is the district average: about 10.7 gpg. That’s under Noritz’s limit, but not by much. South Jordan, also a JVWCD customer, lists 7–10 gpg. In Utah County, American Fork tells residents to set softeners at 12.38 gpg, just over.
If you aren’t sure which side of the line your home is on, your city’s annual water quality report is the place to look. Our Utah hard water guide links many of them.
Seeing a code? Call to book a descale
Noritz codes you might see
| Code | Noritz’s meaning | Likely cause | Safe check for you | When to call |
|---|---|---|---|---|
| C1# | a service reminder for periodic maintenance, such as flushing scale from the heat exchanger | Scale in the heat exchanger after a period of use | Note the full code, including the digit | Book a flush; the warranty depends on it |
| 11 | ignition failure | Gas supply, ignition parts or a closed gas valve | See whether your other gas appliances light | Call; gas work belongs to a technician |
| 90 | a possible blocked air supply or exhaust vent, abnormal combustion, or a clogged condensate drain | Vent or intake blockage, combustion trouble or a blocked drain line | Look for snow or debris at the outside vent, without touching it | Call; venting and combustion need a technician |
For other brands’ scale and flow codes, see the error code hub.
C1#: service reminder for scale
C1# is how a Noritz EZ unit asks to be flushed. The # stands for a digit from 1 to 9. The EZ owner’s guide calls it a service reminder for periodic maintenance, such as flushing scale from the heat exchanger and warns that too much scale may cause the heat exchanger to fail early.
Why does hard water bring it on? The heat exchanger is the set of narrow tubes that the burner heats. Calcium and magnesium in the water drop out as a crust when they get hot, and that crust builds on the inside of the tubes. The crust insulates the metal, so the tubes run hotter, which bakes on more scale. Utah’s water carries more of those minerals than most of the country; Herriman City notes that, according to the USGS, Utah is at the top of the list for hard water.
Because the reminder is optional, some Noritz heaters never show it. If yours has been running for a year or more with no flush and no C1#, that may only mean the reminder was never switched on.
Code 90 and the condensate drain
Code 90 isn’t a scale code, but it’s worth understanding on a condensing heater. EZ units are condensing heaters, which means they make acidic water (condensate) that drains away through a small line. When the guide lists a possible blocked air supply or exhaust vent, abnormal combustion, or a clogged condensate drain, the drain is one of the causes. A technician should handle the venting and combustion checks; you can only safely look for an outside vent that’s obviously blocked.
The Noritz flush, step by step in outline
Noritz’s written flushing procedure is document NCC199. This summary helps you recognize a proper job. It isn’t a do-it-yourself guide, and anything involving gas, venting or electrical power belongs to a technician.
- Valves first. The procedure states that isolation valves are necessary. These are the hot and cold shut-offs on the lines below the heater, with small ports for hoses. No valves means no proper flush; our isolation valve guide explains why.
- The solution. NCC199 calls for 1 gallon of calcium, lime and rust remover plus 1 gallon of water. Noritz’s knowledge base also allows pure vinegar.
- Circulation. A submersible pump pushes the solution through the heat exchanger for 60 minutes, at the flow rate the procedure specifies.
- Rinse. Fresh water runs through for 3 minutes or more to clear out the solution and loosened scale.
The Noritz guide’s own wording is that flushing is periodic, so ask the technician to note the date and to switch on the C1# reminder if it’s off.
Seeing a code? Call to book a descale
Treating Utah water for a Noritz
Noritz doesn’t name its own scale-prevention product in the documents here. What it does say is that water above its limit should be treated. In practice that means a water softener or a scale-prevention cartridge ahead of the heater. Treatment slows scale; it doesn’t replace the flush. See the options on our scale prevention page.
Seeing C1#? Call to book a descale. Flush My Tankless books flushes and repair visits with a local tankless technician. HomeAdvisor says homeowners spend $150–$250 on a tankless flush; the technician sets the actual price.