A tankless heater has no large storage tank to flush, but water still
flows through a heat exchanger. Mineral buildup can reduce performance,
particularly where water is hard. The service procedure depends on the
exact unit, its water conditions, and the manufacturer’s
instructions.
Find the model number and the last service record. Ask whether the
unit has an accessible inlet screen, isolation valves for descaling, and
a condensate drain. Some of these checks are simple observations;
opening gas, vent, or electrical components is for a qualified service
person. Navien’s
manufacturer manuals illustrate why it is better to use the
instructions for the specific model than a generic vinegar recipe from
the internet.
A drop in hot-water flow, an error code, unusual sound, leak, or
recurring condensate issue deserves service. Descaling may be one part
of the visit, not the explanation for every symptom. Have the contractor
check water quality and recommend a schedule suited to the unit, and
keep the work record. Don’t ignore a relief line or venting concern
while focusing on scale.
For local plumbing or water-heater help, see my Helpful
Resources page. My Homeowner
Tools & Supplies guide includes leak detection ideas; any
service kit should be selected against the model manual.