Herriman’s own wells are very hard. The city says they usually measure 25–60 gpg, which is two to five times the 12 gpg limit Noritz publishes. The water Herriman buys from the Jordan Valley district is much softer, and the city leans on it in the off-season for that reason. For a tankless owner, that likely means faster scaling in the months the wells are in use, and a case for flushing more often than once a year unless the water is treated. HomeGuide’s advice for hard-water homes is every 6 to 9 months.
Two waters, one tap
Herriman’s 2025 water quality report says the city supplies water from five wells, one spring, Jordan Valley Water Conservancy District and Bluffdale City, drawing on ground and surface sources. Those sources are not alike.
In a November 2025 post on the city’s blog, Herriman described the gap. Its local wells are very hard, usually 25–60 gpg. The Jordan Valley water it buys generally measures 12–15 gpg, which the city calls much softer than its wells.
The 2025 report shows the same spread in another way. Total dissolved solids (TDS) across Herriman’s sources ran ND–1632 ppm in 2025 monitoring (ND means not detected). TDS isn’t hardness, but a range that wide confirms how different the sources are.
The mid-October switch
Because the wells are so hard, Herriman changes its supply each year. In mid-October, the city switches to Jordan Valley water only for the off-peak season. The city doesn’t say exactly when the wells come back on, but switching to district water only for the off-peak season suggests the wells are part of the mix the rest of the year.
That has a direct effect on your water heater. In the off-peak months, it’s running on district water. During the high-demand season, some of what reaches your house may be well water at several times the hardness, and scale can build faster while it is. If you flush once a year, doing it in fall, after the heavy-use months and around the switch, clears the summer’s build-up.
What Herriman and the district each say
The two published figures for the district’s water don’t match:
- Herriman City says the Jordan Valley water it buys generally measures 12–15 gpg.
- Jordan Valley Water Conservancy District says on its website that its water can range anywhere from 1–12 gpg.
We don’t know which is closer for a Herriman tap, and we won’t pick one. The ranges barely touch, so the safe reading is that even Herriman’s winter water may sit at or above the 12 gpg limit Navien and Noritz publish. Herriman also points out that, according to the U.S. Geological Survey, Utah is at the top of the list for hard water in the United States.
What this means for each brand
On well water, no brand comes close. Takagi’s limit is 7 gpg, Bosch’s is 100 ppm, Rinnai’s is 200 ppm and Navien’s is 12 gpg. Herriman’s wells start at roughly double the most lenient of those.
Warranty language follows. Rheem’s warranty says damage caused by lime, mineral build-up, or scale is excluded, and Rinnai’s excludes improper maintenance such as scale build-up. In Herriman, a softener or a manufacturer’s scale-prevention system is the main thing standing between a tankless heater and an uncovered heat exchanger failure.
Watch the display, too. On a Rheem, code 1L means lime build-up has been detected in the heat exchanger. Rinnai’s LC is easy to ignore, because Rinnai notes it is the only code that lets the unit keep running: the heater alternates between LC and the temperature setting and carries on while the scale keeps building. In Herriman, treat either code as a call to book a flush, not a suggestion.
Bluffdale
Bluffdale, Herriman’s neighbor to the southeast, is a simpler case. The city buys its water from the Jordan Valley Water Conservancy District, and Herriman itself lists Bluffdale City among its own suppliers. Bluffdale’s 2025 report says the district uses surface water and groundwater: the Provo River watershed, local mountain streams and wells in the southeast valley.
The Jordan Valley data in Bluffdale’s 2025 report show an average total hardness of 184.1 mg/L, or about 10.8 gpg. That’s past the USGS “very hard” line but within the Navien, Noritz, Rinnai and Rheem limits, and over the Takagi, A.O. Smith and Bosch limits. The same report lists average total dissolved solids of 292.5 mg/L.
Bluffdale’s report describes no seasonal switch like Herriman’s, so for most Bluffdale tankless owners a yearly flush is the reasonable baseline. Bluffdale requests go through this page.
Tankless services in Herriman
- Flush and descale: a fall flush, after the high-demand months, is a sensible habit here.
- Annual maintenance: adds filter cleaning and a broader check to the flush.
- Repair: for the overheat and scale codes that hard water leads to.
- Installation: plan treatment alongside any new heater.
- Scale prevention: the single most useful step for a Herriman tankless.
For cost, HomeGuide gives $150–$350 per professional flush. With a schedule closer to twice a year, the yearly total roughly doubles, which is part of the case for treatment.