Hard water, winter sizing, and permits

Hard water

• Provo: 10 to 15 grains per gallon, which the city's 2025 water report calls moderately hard.
• Orem: 7 to 25 grains per gallon across the city's own springs and wells.
• American Fork: the city suggests setting your water softener to 12.38 grains per gallon.

Lab reports often give hardness in milligrams per liter instead. One grain per gallon equals about 17.1 mg/L, so Provo's range works out to about 171 to 257 mg/L, and the top of Orem's well range is 428 mg/L.

The U.S. Department of Energy's tankless guide says scale "can restrict the flow of water through the heat exchanger and diminish the life of the unit." It also says that where hardness exceeds 8 to 14 grains per gallon, manufacturers may require a water softener. Rinnai's Value Series manual lists a total hardness limit of 200 mg/L, about 11.7 grains per gallon. The upper end of Provo's range and the upper part of Orem's well range sit above that limit.

Your choices:

• Whole-house softener. Treats all the water in the house, including the tankless unit. Salt-based softeners need regular refills.
• Scale filter or inhibitor ahead of the unit. Protects only the water heater. Check that the manufacturer accepts it as meeting its water-quality requirement.
• No treatment, more flushing. DOE puts the flushing interval anywhere from twice a year to once every three years, depending on water quality. With hard water, plan on the short end.

Rinnai's residential warranty excludes damage from scale build-up and from poor water quality. Read the terms for the model you're buying before you skip treatment. The flushing guide covers the routine step by step.

Cold winters

NOAA's 1991-2020 climate normals for the Provo BYU station give a January average of 32.5°F and a normal January low of 23.8°F. The station averages 44.9 inches of snow and 4,968 heating degree days a year.

Air temperature doesn't tell you the temperature of the water entering the house, and that water sets a tankless unit's flow. The sizing guide shows how to measure it on a January morning.

Codes and permits

Utah adopts one construction code for the whole state, and each city's building department enforces it. Utah Code 15A-2-103 adopted the 2021 International Residential Code, the 2024 International Plumbing Code, and the 2024 International Fuel Gas Code, effective July 1, 2026. Utah Code 15A-3-205 adds statewide amendments, including a rule that water heaters be anchored or strapped against earthquake motion.

IRC section R105.1 requires a permit to install, convert, or replace a gas or plumbing system. Provo, Orem, Spanish Fork, Highland, Alpine, and Springville name water heaters on their own pages. Springville's permit-exemption sheet also reprints IRC R105.2.1: when a water heater has to be replaced in an emergency, the permit application goes in by the next working business day.

Provo asks for a gas line diagram with permits for tankless units, and lists a $75 base fee for standard trade permits plus a $12 processing fee. Other cities set their own fees. The cities page summarizes what each city's own page says.

Gas appliance rules for do-it-yourselfers

Utah exempts property owners doing work on their own property from contractor licensing, under conditions set in Utah Code 58-55-305. Gas appliances carry an extra rule. Utah Code 58-55-308 says a person who installs, repairs, or replaces a residential gas appliance must first complete training and certification under state rules, and that applies to people otherwise exempt from licensing. A permit and inspection still apply. Utah is renumbering these sections on January 1, 2027, so the citations will change.

The license guide explains how to look up an installer's license with the state. The contact page sends your request to an independent local contractor.