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Tankless Water Heater Problems in Mission Viejo: 6 Common Fixes
Tankless units are reliable, but hard water and venting problems catch up with them. Here are the six problems we see most and what fixes them.
Call Now – (949) 693-0298In this guide
- Scale buildup from hard water
- Error code on the display
- Cold water sandwich
- Won't ignite or flame goes out
What are the most common tankless water heater problems?
The six problems we see most on tankless units are mineral scale buildup, error codes, a burst of cold water between hot (the cold water sandwich), ignition failure, not enough hot water when two fixtures run, and a clogged inlet filter. Many trace back to Orange County's hard water. Most are fixed with a flush, a filter cleaning or a part replacement. Call (949) 693-0298.
Our tankless water heater repair mission viejo ca techs work on Rinnai, Navien, Noritz, Rheem and other brands every week.
Why does hard water cause tankless problems?
Water in South Orange County is hard, which means it carries calcium and magnesium. When a tankless unit heats water, those minerals form scale inside the heat exchanger. Scale makes the unit work harder, cuts hot water flow and can trigger error codes. Most makers recommend flushing, or descaling, about once a year, and more often with very hard water.
A yearly descaling is part of our water heater maintenance and flushing service. A tank flush on a standard water heater costs about $120 to $250.
What should you do when the unit shows an error code?
Write down the code, then check the owner's manual or the label inside the cover. Many codes point to simple causes, like a closed gas valve, a clogged filter or low water flow. Turn the unit off and on once to reset it. If the code comes back, call a technician, because repeat codes often mean a sensor, fan or ignition part has failed.
- Ignition or flame codes: check that the gas valve is open and other gas appliances work.
- Overheat or scale codes: the heat exchanger likely needs descaling.
- Flow or sensor codes: clean the inlet filter and check for low water pressure.
- Venting codes: the vent may be blocked by a nest, debris or a bad joint.
Smell gas? Leave the home right away, then call 911 and the SoCalGas 24-hour line at 1-877-238-0092 from outside.
What is the cold water sandwich?
The cold water sandwich is a short burst of cold water between two bursts of hot. It happens when you turn the hot water off and back on quickly, like during a shower. Hot water left in the pipes comes out first, then cold water passes through while the unit fires again. It is normal on many units, though a recirculation pump or a small buffer tank can reduce it.
If the water goes cold for a long time instead of a few seconds, the unit may be shutting down from scale, low flow or an ignition problem.
Why is there not enough hot water?
A tankless unit can only heat so many gallons per minute. If two showers and the dishwasher run at once, the unit may not keep up, so the water goes lukewarm. Scale buildup and a clogged inlet filter also cut flow. If it happens often, the unit may be too small for your home, or it needs a descaling.
Try running one less fixture at a time to test it. If one shower alone is lukewarm, the unit needs service.
Why won't the tankless water heater ignite?
If the unit will not light, check that the gas valve is open, the unit has power and the venting is clear. Then check that other gas appliances work. If they do, the problem is usually the igniter, the flame sensor, the gas valve or a dirty burner. These parts should be serviced by a technician.
Small parts like an igniter usually cost about $150 to $300 to replace. A gas control valve runs about $350 to $650.
How do you keep a tankless water heater running well?
Descale the unit about once a year, or more often with hard water. Clean the inlet water filter every few months. Keep the area around the unit and the vent clear. Make sure the gas line is sized for the unit. Write down any error codes so the technician can see a pattern.
- Flush or descale every 6 to 12 months.
- Clean the cold water inlet filter.
- Check the outdoor vent cap for nests and debris.
- Consider a water softener or scale filter if scale keeps coming back.
Many units have isolation valves that make yearly descaling quick. If yours does not, a technician can add them.
Is it worth repairing a tankless water heater?
Usually, yes. Tankless units often last 15 to 20 years, so most repairs on a unit under 10 to 12 years old are worth it. Water heater repair in Mission Viejo usually costs about $150 to $650. If the heat exchanger has failed on an older unit, replacement may make more sense. A tankless install runs about $3,800 to $7,500.
If you are weighing a new unit, see our water heater replacement cost guide. We also serve water heater repair Lake Forest homeowners and the rest of South Orange County.
Frequently asked questions
How often should a tankless water heater be flushed?
Most makers recommend about once a year. With hard water, every 6 to 12 months is common.
Why does my tankless water heater keep going cold?
The most common causes are scale buildup, a clogged inlet filter, low flow, too many fixtures at once, or an ignition problem.
Can I reset my tankless water heater?
Yes. Turning it off and on once can clear some codes. If the code comes back, call a technician.
How much does tankless water heater repair cost in Mission Viejo?
Most water heater repairs cost about $150 to $650. A tankless install runs about $3,800 to $7,500.
Talk to a water heater pro now
Questions about your water heater? Call a local pro in Mission Viejo, CA. Open 24 hours a day, 7 days a week.
(949) 693-0298 Call Now – (949) 693-0298