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Tankless water heater maintenance mostly means flushing the heat exchanger once a year to dissolve mineral scale. You also clean the inlet water filter, check the air intake and vent, and test the pressure relief valve. Homes with hard water or a private well may need a flush every six months.
A tankless unit needs little attention, but scale is the one thing it can’t handle on its own. Our tankless water heater service team is certified on Navien and Rinnai units and works on homes across High Point, Greensboro, Winston-Salem and the rest of the Triad. Call (336) 462-1080 and a real person will answer, day or night.
Key Takeaways
- Scale is the main enemy. Minerals in your water build up inside the heat exchanger and slowly choke flow and heat transfer.
- Flush once a year. Most manufacturers call for an annual descaling flush, and more often with hard or well water.
- Small parts matter too. The inlet filter screen, air intake and vent all need a quick look at every service.
- DIY is possible. A handy homeowner with service valves, a small pump and the right solution can flush a unit in about an hour or two.
- Know when to stop. Gas smells, repeated error codes or leaks at the gas line are jobs for a licensed plumber.
What Does Tankless Water Heater Maintenance Involve?
A tankless water heater has no tank to collect sediment. Instead, water flows through a coiled heat exchanger and gets heated on demand. That design saves space, but it puts every mineral in your water right against the hottest surface in the unit.
Tankless water heater maintenance is the routine that keeps that heat exchanger clean and the safety parts working. It has four main parts:
- Descaling flush. A pump circulates a descaling solution through the heat exchanger to dissolve built-up minerals.
- Inlet filter cleaning. A small screen on the cold water inlet catches grit before it reaches the unit.
- Vent and air intake check. Gas units need clear venting so combustion gases leave the house safely.
- Relief valve test. The pressure relief valve has to open freely if pressure ever climbs too high.
Tankless vs Tank Maintenance
A traditional tank heater gets drained to remove sediment from the bottom of the tank. A tankless unit gets flushed with a circulating solution instead. Draining alone does not remove hard scale stuck to the heat exchanger walls.
Why Hard Water Makes Maintenance Matter in the Triad
Hard water is water high in dissolved calcium and magnesium. The USGS water hardness guide explains that when hard water is heated in a home water heater, calcium carbonate deposits can form. That scale can shorten equipment life, raise the cost of heating water and clog pipes.
The USGS classifies water by how much calcium carbonate it carries:
| USGS hardness class | Calcium carbonate (mg/L) | What it means for a tankless unit |
|---|---|---|
| Soft | 0 to 60 | Annual flush is usually enough |
| Moderately hard | 61 to 120 | Stick to a yearly flush without fail |
| Hard | 121 to 180 | Consider a flush every six months |
| Very hard | More than 180 | Flush every six months and look at water treatment |
City Water vs Private Well
Where your water comes from changes how fast scale builds. According to the High Point water report, the city’s water comes from rainfall and runoff collected in two lakes, Oak Hollow and Arnold Koonce City Lake. That water is treated before it reaches your tap.
Private wells are a different story. The USGS notes that groundwater dissolves minerals as it moves through soil and rock, so well water is often harder. Part of the Triad runs on private wells, and tankless units on well water usually need more frequent flushing.
How Often Should You Do Tankless Water Heater Maintenance?
Once a year is the standard schedule for most homes. Use this table as a starting point, then follow your owner’s manual.
| Task | City water | Private well or hard water |
|---|---|---|
| Descaling flush | Every 12 months | Every 6 months |
| Clean inlet filter screen | Every 6 to 12 months | Every 3 to 6 months |
| Check vent and air intake | Every 12 months | Every 12 months |
| Test pressure relief valve | Every 12 months | Every 12 months |
If you want us to handle the schedule for you, our annual water heater maintenance visit covers both tank and tankless units.
Signs Your Tankless Unit Needs a Flush
A scaled-up heat exchanger usually gives you warnings before it quits. Watch for these:
- Water that swings between hot and cold during a shower
- Lower hot water flow than you used to get
- Longer waits for hot water at the tap
- Error codes on the display that point to overheating or flow problems
- A whistling, popping or rumbling noise while the unit runs
- White, chalky buildup on faucets and showerheads
That chalky crust on fixtures is one of the most common hard water signs, and it means the same minerals are collecting inside your heater.
How to Flush a Tankless Water Heater, Step by Step
You will need a flush kit (a small submersible pump and two washing machine style hoses), a 5-gallon bucket and a descaling solution. Most manufacturers allow food-grade white vinegar or their own approved descaler. Always check your owner’s manual first, because some models have specific rules.
- Shut off power and gas. Unplug the unit or turn off its breaker. On a gas model, close the gas valve to the heater.
- Close the isolation valves. Turn off the cold inlet and hot outlet service valves so no water flows through the house lines.
- Relieve the pressure. Open a hot water faucet in the house, then slowly open the purge ports on the service valves with a bucket below.
- Connect the hoses. Run one hose from the pump to the cold side purge port. Run the second hose from the hot side purge port back into the bucket.
- Add the solution and circulate. Pour 2 to 4 gallons of vinegar or descaler into the bucket, set the pump in it and let it run for 45 to 60 minutes.
- Rinse with fresh water. Dump the used solution, then open the cold isolation valve and let clean water run through the unit and out the hot side hose for about five minutes.
- Clean the inlet filter. Close the cold valve, unscrew the small filter screen near the cold inlet, rinse it under the tap and put it back.
- Restore service. Close the purge ports, open both isolation valves, run a hot faucet until the air clears, then turn the gas and power back on.
If your unit has no service valves, stop here. Installing them means cutting into the water lines, and that is a job for a plumber.
Rather not tackle the flush yourself? Call (336) 462-1080 and we can flush and inspect your unit for you. You approve the upfront price before any work begins, and there is no charge if you decline the quote.
Other Care Tips Between Flushes
- Keep the vent clear. Check outside vent caps for leaves, nests and snow, especially after winter storms.
- Wipe the air intake. Dust and lint can collect on the intake screen in garages and laundry rooms.
- Protect it from freezes. Units mounted on exterior walls or in unheated spaces need freeze protection when Triad winters dip below freezing.
DIY or Professional: Which Should You Choose?
A basic flush is a fair DIY job if your unit already has service valves and you are comfortable with hoses and a pump. A professional visit adds checks most homeowners skip, like gas pressure, combustion and vent connections, and a look at the error history.
| Option | Typical national cost range | Good fit when |
|---|---|---|
| DIY flush | About $50 to $150 for a pump kit and solution | Service valves are installed and the unit runs normally |
| Professional flush and inspection | About $150 to $350 | You want a full safety check or have never had the unit serviced |
| Repair after scale damage | Varies widely by part | Error codes keep coming back after a flush |
These are typical national ranges, not our prices. Your final price is confirmed upfront before any work starts. If scale keeps coming back fast, a water softener can help, and our guide to hard water treatment options walks through the choices.
When to Call a Plumber Right Away
- You smell gas near the heater
- Water is leaking from inside the cabinet
- The same error code returns after a flush
- The vent pipe is cracked, loose or separated
If you are near Greensboro, our plumbers serving Greensboro answer the phone around the clock and can check the unit for you.
Tankless Water Heater Maintenance FAQs
Do you have to maintain a tankless water heater?
Yes. A tankless water heater needs a descaling flush at least once a year, plus filter cleaning and a vent check. Skipping it lets scale build in the heat exchanger, which cuts flow, causes temperature swings and can trigger error codes or early failure.
How long does it take to flush a water heater?
A tankless flush takes about one to two hours, including 45 to 60 minutes of circulating the descaling solution and a fresh water rinse. A standard tank water heater drain usually takes less time, though a tank with heavy sediment can take longer to clear.
How often should you drain your water heater?
Drain or flush a tank or tankless water heater once a year on city water. Homes with hard water or a private well should flush a tankless unit every six months. Your owner’s manual may list a specific schedule for your model, so check it first.
How much do plumbers charge to drain a water heater?
A professional tankless flush and inspection usually falls around $150 to $350 as a typical national range. The price depends on access, how much scale is present and whether service valves need to be added. A good plumber confirms the price with you before starting.
Keep Your Tankless Unit Running With a Yearly Flush
Regular tankless water heater maintenance keeps hot water steady, protects the heat exchanger and helps your unit reach its full service life. One flush a year, or two on hard or well water, is a small job compared with replacing a scaled-up heater.
All-Star Plumbing of the Triad has been family owned in High Point since 2007, and our phone is answered 24/7 by a real person. Call (336) 462-1080 to book a tankless flush and inspection. If we can’t fix it, you don’t pay.
All Star Plumbing
4003 North Main Street, High Point, NC 27265
Phone: (336) 462-1080
Hours: Open 24/7
NC Plumbing License #15130
