Tankless Water Heater Repair and Installation in Raleigh
Error code on the display, water that goes hot then cold, or a unit that won't fire? Here is what usually causes tankless problems, what to check, and what to know if you are thinking of switching to tankless.
Free referral and information service. How it works
- Gas and electric tankless
- Error codes and descaling
- Install and conversion questions
Most tankless problems come from scale or debris in the heat exchanger or inlet filter, venting or gas supply issues, low flow, or a failed sensor, igniter or flame rod. The error code on the unit is the best clue. Tankless units heat water as it flows, and DOE puts their output at about 2 to 5 gallons per minute, so running several fixtures at once can outpace a single unit.
Tankless heaters last longer than tanks (about 20 years, per DOE) but need regular maintenance. Many manufacturers call for periodic descaling. Raleigh's city water is classified as soft (about 1.4 to 1.5 grains per gallon in the city's 2025 water quality report), which helps, but private wells and other water sources vary.
Write down the brand, model and the exact error code before you call. Many codes have a specific meaning in the owner's manual.
Common tankless problems
Cold-water bursts
Brief cold water between uses is common with tankless. Persistent swings can mean low flow, scale or a sensor problem.
Error code on the display
Codes point to ignition, flame, venting, overheating or flow faults. Note the exact code for the plumber.
Unit won't ignite
Gas supply, igniter, flame rod, venting or condensate drain problems can all stop a gas unit from firing.
Not hot enough with two showers
The unit may be undersized for the flow you need, or scale is reducing its output.
What to check first
- Note the error code and the model number from the unit label.
- Check power to the unit (it needs electricity even on gas models) and that the gas supply is on.
- Try one fixture at a time to see if the problem is flow-related.
- Look at the inlet filter if the manual shows how to clean it safely. Close the water valves first.
- Don't open the unit cover. There are gas, electrical and combustion parts inside. Leave that to a plumber.
What a plumber does on a tankless call
- Reads the error history and checks gas pressure, venting and the condensate drain on condensing units.
- Descales the heat exchanger by flushing it through the service valves, if scale is the cause.
- Cleans the inlet filter and checks flow sensors.
- Tests ignition parts such as the igniter and flame rod, and replaces failed parts.
- Checks sizing against the flow your household actually uses.
Questions to ask the plumber
- Have you serviced my brand of tankless heater before?
- What does the error code mean, and what will you replace?
- Is scale part of the problem, and how often should I descale?
- Is my unit sized right for my household?
- Does the price include parts, labor and any return visit?
Switching from a tank to tankless
Going tankless frees up space and can cut standby energy losses, but the install is more involved than a tank swap. Gas units often need a larger gas line and new venting. Electric tankless units can need significant electrical capacity. Ask the plumber to check your gas meter, line size, panel and vent route before you commit. See water heater replacement for permits and sizing.
Pros and cons
- Pros: longer life (about 20 years per DOE), compact, no tank to leak, hot water on demand.
- Cons: higher install cost, limited flow per unit, needs regular descaling, a short delay or cold burst between uses.
Tax credits
Federal home-energy credits changed for equipment placed in service after 2025. Don't assume a credit applies. Check current IRS guidance or ask a tax professional before you count on one.
Frequently asked questions
How often should a tankless water heater be descaled?
Follow the manufacturer's schedule in the owner's manual. It depends on water hardness and use. Raleigh city water is classified as soft, but well water can be much harder.
Why does my tankless water heater go cold in the middle of a shower?
Common causes are low flow (for example a low-flow shower head below the unit's minimum), scale, a dirty inlet filter, gas supply problems or too many fixtures running at once.
How long do tankless water heaters last?
The U.S. Department of Energy says about 20 years, compared with about 10 to 15 years for a tank.
Is tankless worth it in Raleigh?
It depends on your household, fuel and how long you will stay in the home. It costs more to install than a tank but lasts longer. Ask a plumber to compare both for your house.
Can a tankless water heater be repaired, or does it need replacing?
Many tankless problems are fixed with descaling, cleaning or replacing a sensor or igniter. A cracked or badly scaled heat exchanger can be a bigger repair, and the plumber will compare that with replacement.
Related help
No hot water or a leaking tank?
Turn off the power or gas to the heater and close the cold-water valve above it if water is leaking. Then get help from an independent local plumber.