Tankless units are built to be serviced
Unlike a tank, which is usually replaced once it leaks, a tankless unit is made of replaceable parts: igniters, sensors, fans, circuit boards, valves and filters. A failed part does not automatically mean a failed heater.
The exception is the heat exchanger. If it leaks, or has been badly damaged by years of scale in Fullerton's hard water, replacing it can be a large share of the cost of a new unit. That is where the repair-or-replace question gets serious.
Common situations
- IfA sensor, igniter or fan has failed on a younger unitThenRepair is usually reasonable if parts are available.
- IfThe heat exchanger leaks and the unit is out of warrantyThenCompare the repair cost with a new unit before deciding.
- IfThe unit is older and parts are discontinuedThenReplacement may be the practical choice.
- IfScale codes keep returning even after flushingThenAsk whether the heat exchanger is damaged, and set up a proper flushing schedule either way.
- IfThe original install has venting or gas problemsThenFix the installation issues first; a new unit on the same faults will struggle too.
What drives the decision
| Factor | Points toward repair | Points toward replacement |
|---|---|---|
| Age | Well within its expected service life | Near or past the manufacturer's expected life |
| Failed part | Sensor, igniter, valve, fan, filter | Heat exchanger, or several major parts at once |
| Warranty | Part or labor still covered | Coverage expired |
| Parts | Readily available | Discontinued or hard to source |
| Installation | Gas, vent and valves are sound | Undersized gas, poor venting, no service valves |
Before you decide
- Find the paperwork.Locate the model number, serial number, install date and warranty registration.
- Get a diagnosis.Ask the plumber to identify the failed part and show you the evidence, such as an error history or a visible leak.
- Check warranty coverage.Contact the manufacturer with the serial number to see what is still covered and who may perform warranty work.
- Compare in writing.Get the repair scope and a replacement scope side by side, including any gas or vent changes.
Ask the plumber
- Which part failed, and how did you confirm it?
- Is the heat exchanger in good condition?
- Are parts available for this model?
- If we replace, what changes would you make to the gas, venting or valves?
Common questions
How long do tankless water heaters last?
Service life depends on the model, water quality and maintenance. Check the manufacturer's guidance and warranty terms for your unit.
Does scale damage void the warranty?
Some manufacturers limit coverage for damage from scale or missed maintenance. Read your warranty terms.
Can I switch back to a tank?
Yes. The gas, vent and space needs differ, so have a plumber scope it like any other installation.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.