Navien Tankless Water Heater Maintenance and Descaling in Chicagoland

Why hard water is the issue in Chicagoland

Water in this area carries dissolved minerals, mostly calcium and magnesium. When that water is heated, some of those minerals come out of solution and deposit on the hottest surfaces they touch. In a tank water heater that sediment settles harmlessly on the bottom for years. In a tankless unit, the hottest surface is the inside of the heat exchanger — the exact passage the water has to flow through.

Scale inside the exchanger does three things at once. It narrows the passage, so flow drops. It insulates the metal from the water, so the burner has to fire harder and longer for the same outlet temperature. And it creates hot spots that stress the exchanger itself. None of that is dramatic on day one; it accumulates quietly until the unit starts throwing codes or the shower stops holding temperature.

Homes with a working water softener build scale much more slowly. Homes without one, which is most of the housing stock we see in the older suburbs, build it faster.

What descaling a tankless water heater actually involves

Descaling — sometimes called flushing — means circulating a cleaning solution through the heat exchanger to dissolve mineral buildup, then rinsing it out. It is not the same as draining a tank.

• Shut down the unit and close the isolation valves on the hot and cold connections
• Connect hoses and a small pump to the service ports on those valves
• Circulate a descaling solution through the heat exchanger for a set period
• Flush with clean water until it runs clear and the solution is fully rinsed out
• Clean the cold water inlet filter screen, which catches grit and reduces flow when clogged
• Reopen the valves, purge air, and confirm the unit fires and holds its set temperature

How often should a tankless unit be descaled?

About once a year is the right planning interval for most Chicagoland homes, and manufacturers generally recommend annual service in hard water. A few situations justify going more often.

• Large households running back-to-back showers and laundry every day
• Restaurants, salons, gyms and other commercial hot water loads
• Homes with no water softener and noticeably heavy scale on fixtures and glass
• Any unit that has already thrown a scale-related error code once
• Cascaded commercial systems, where one unit falling behind loads the others

Warning signs your tankless heater is overdue for service

None of these mean the unit is finished. Most of them mean it is asking for maintenance, and maintenance is far cheaper than a heat exchanger.

• Hot water that starts strong and fades, or swings between hot and lukewarm
• Lower flow at the showerhead than the unit used to deliver
• The heater locking out and needing a reset more than occasionally
• Error codes on the panel, especially any that reference flow, temperature or the exchanger
• Rumbling, popping or a rougher-sounding burner cycle
• A longer wait for hot water than you remember
• No documented service in the last two years

What else a full maintenance visit should cover

Manufacturers typically tie warranty coverage to documented maintenance, so keeping records of annual service protects the equipment and the coverage at the same time.

• Burner and combustion inspection, including the flame sensor and igniter
• Venting and intake check for blockage, slope, and correct termination clearances
• Condensate trap and neutralizer condition on condensing models
• Gas pressure verification under load
• Inlet filter and any in-line strainers
• Stored error history from the control board, which often explains an intermittent complaint
• Confirmation of the temperature setting and any recirculation settings

Can a homeowner descale a tankless water heater?

Some homeowners do, and with isolation valves already installed, a flush kit and careful attention to the manufacturer's instructions, it is within reach for a handy owner. What a DIY flush does not include is the combustion, venting, gas pressure and error-history side of the visit, which is where the safety-relevant findings usually turn up.

If your unit is under warranty, is showing codes, is vented through a long or complicated run, or has never been serviced, have it done professionally at least once so you know the baseline condition of the equipment.

Right Away handles tankless maintenance, descaling, repair and replacement across the area — see our tankless water heater service and installation page for what a visit includes and how to schedule one.

Frequently asked questions