No hot water is never a minor inconvenience, and when it comes from a tankless unit, the cause is usually something specific that a trained plumber can diagnose and fix quickly. Tankless systems are built to last, but they do develop problems over time, and those problems tend to show up as error codes, fluctuating temperatures, or a complete loss of hot water. Our team works on all major tankless brands across Goose Creek and the Tri-County area, and same-day service is available for most repair calls. If your unit isn’t performing the way it should, call us at (843) 572-8522 and we’ll get it sorted out.
Tankless water heaters fail in recognizable patterns. Here are the issues we see most often.
This is the most alarming situation and usually points to an ignition failure, a gas supply issue, a flow sensor problem, or a tripped error code that has locked the unit out.
This is the brief burst of cold water you get between two streams of hot water. It happens when residual hot water in the pipes runs out, the unit fires up, but there's a delay before the newly heated water reaches the fixture. It's normal in small doses but can indicate a problem with flow rate or unit response if it happens frequently.
Most tankless units display error codes when something is wrong. These codes point directly to the system or component that needs attention.
Low flow through the unit can prevent the unit from firing at all. It can also cause temperature swings if the flow rate drops below the unit's minimum activation threshold.
Popping, banging, or rumbling sounds from a tankless unit often indicate scale buildup inside the heat exchanger. This is one of the most common maintenance-related issues in areas with harder water.
Water pooling near the base or along connections is a sign of a loose fitting, a failed seal, or a damaged component inside the unit.
The unit calls for hot water but fails to fire. This can be caused by a gas supply issue, a dirty flame sensor, a blocked flue, or a failed ignition component.
Improper venting or a blocked flue causes the unit to shut down as a safety measure. If your unit shuts off repeatedly without a clear cause, ventilation is worth checking.
Error codes take the guesswork out of diagnosing what’s wrong. Here are the most common ones we see across the brands we service.
Code | Issue |
11 | No ignition: gas supply or ignition system |
12 | Flame failure during operation |
14 | Thermal fuse has blown: overheating |
25 | Condensate neutralizer issue |
31 | Inlet thermistor fault |
32 | Outlet thermistor fault |
61 | Combustion fan failure |
Code | Issue |
E003 | Ignition failure |
E012 | Flame loss during operation |
E016 | Overheating detected |
E027 | Air pressure switch fault |
E036 | Cold water inlet thermistor fault |
E040 | Exhaust thermistor fault |
Code | Issue |
P1 | Cold water flow sensor issue |
P3 | Hot water thermistor fault |
C7 | Venting or combustion issue |
13 | Gas valve failure |
15 | Flame sensor fault |
These are starting points for diagnosis. In many cases, a code points to a specific component, but the underlying cause may be something related. We run a full diagnostic on every unit before ordering parts or making repairs.
Some problems are obvious. Others show up gradually before the unit stops working entirely. Here are the signs to watch for.
If the water shifts between hot and cold while you’re in the shower, the flow sensor, thermistor, or heat exchanger may be the issue.
In areas with harder water, scale accumulates inside the heat exchanger over time. You may notice the unit running longer to reach temperature, reduced flow at hot water fixtures, or strange noises from inside the unit.
If you’re getting less flow from hot water fixtures than from cold, the restriction is likely inside the unit rather than in the supply line.
Some delay is normal for tankless units. A delay that has gotten noticeably longer over time often points to a scaling issue or a degraded component.
If an error code comes back after you reset the unit, the underlying issue hasn’t been resolved and needs a proper diagnosis.
A sulfur or gas smell near the unit is a gas supply or connection issue and should be treated as an emergency. Turn off the gas supply and call immediately.
Any visible leak around the unit needs to be addressed before it damages the surrounding wall or floor structure.
Not every tankless repair is worth doing. Here’s how we think through the decision honestly.
If the unit is fewer than ten years old and the repair cost is below 40 to 50 percent of a new unit’s installed cost, repair almost always makes sense. If the unit is older than 15 years and a major component like the heat exchanger has failed, the math often points toward replacement instead. Heat exchanger replacement on an older unit can cost as much as a new installation when you add in labor and parts.
We give you the repair cost and the replacement cost side by side so you can make the decision with full information. We don’t push replacement when repair is the right answer, and we don’t recommend a repair that’s going to cost nearly as much as starting fresh.
Our team services all major residential tankless water heater brands, including Rinnai, Navien, Rheem, A.O. Smith, Noritz, Bosch, Bradford White, and Takagi. If you have a unit from one of these manufacturers or another brand not listed here, call us and we’ll let you know if we can service it.
In many cases, we can narrow down the likely cause based on the error code and the symptoms you describe before we arrive. This helps us come prepared with the right parts.
We run through the unit systematically, checking the gas supply, ignition system, flow sensors, thermistors, heat exchanger condition, and venting to identify exactly what’s wrong.
You get a clear repair estimate before any work begins. No surprises after the job is done.
We complete the repair using quality replacement parts, or perform a descaling flush if mineral buildup is the cause of the problem.
After the repair, we run the unit through multiple test cycles to confirm it’s firing consistently, heating to the set temperature, and showing no error codes.
Before we leave, we go over what maintenance the unit needs and how to avoid the same issue coming back.
Repair costs vary based on what’s wrong and which components need to be replaced. Here are the general ranges for common repairs.
We provide a written estimate after the diagnostic so you know the exact cost before we proceed.
We work on all major tankless brands and carry common parts for the units we service most often. Our diagnostic process is thorough, which means we find the actual cause of the problem rather than replacing parts until something works. Pricing is clear before any repair begins. Our team has been serving Goose Creek homeowners for more than 30 years and we’re available for same-day service on most repair calls. When your unit isn’t working, you shouldn’t have to wait several days to get it looked at.
Error codes are the unit’s way of telling you what system or component has detected a problem. Common causes include ignition failure, overheating, sensor faults, and venting issues. The code is a starting point for diagnosis, not always the complete answer. A plumber who services your brand can interpret the code and identify the underlying cause.
In most cases, annual descaling is recommended for areas with moderately hard water. If your water is particularly high in mineral content, descaling every six months keeps the heat exchanger running efficiently. Going too long between descaling cycles reduces efficiency and shortens the life of the heat exchanger.
Some minor issues, like clearing a clogged inlet filter, are manageable for a homeowner with basic mechanical skill. Most repairs, including anything involving gas connections, internal components, or error code diagnosis, should be handled by a licensed plumber. Working on gas connections without the right training and tools creates a real safety risk.
Most repairs are completed in one to two hours once we’re on-site. Jobs that require a part not in stock may take an additional day if we need to source the component. We let you know during the phone diagnostic if that’s likely to be the case.
It depends on the age of the unit, the cost of the repair, and the condition of the rest of the system. We give you both the repair cost and the replacement cost so you can make an informed decision. Units under ten years old with a contained, single-component failure are almost always worth repairing. Units over 15 years old with a major failure like a heat exchanger breakdown are often better replaced.
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