Tankless Water Heater Pinhole Leak? Las Vegas Repair Advice

The short answer

A leak at a fitting, an isolation valve, or the pressure relief valve is a straightforward repair. A genuine pinhole in the heat exchanger itself is usually not worth repairing, and the real question becomes whether the unit is still under warranty, because heat exchangers often carry a longer warranty term than the rest of the unit. First, confirm it is actually a leak: a condensing unit produces water as a normal byproduct, and a blocked or disconnected condensate drain looks exactly like a leaking heater.

Rule out condensate before anything else

A high-efficiency condensing tankless unit extracts so much heat from the exhaust that water vapor in it condenses back to liquid. That water is supposed to leave through a condensate drain line. It is mildly acidic, which is why many installations include a neutralizer in that line.

If the condensate line is kinked, clogged, disconnected, or draining uphill, that water ends up on the floor or pooled in the cabinet. It looks like the heater is leaking. It is not. Check the drain line before you accept any diagnosis that involves replacing the unit.

Follow the small drain line from the unit and check it is clear, sloped downward, and actually connected at both ends.
If there is a neutralizer cartridge in the line, check whether its media is spent or packed solid.
Look at whether the water is clean and appearing only while the unit runs, which fits condensate, or present continuously, which fits a supply leak.

Where the water is coming from decides the job

Source	What it means	Worth repairing?
A threaded fitting or union at the water connections	A seal or thread sealant has failed, or a connection has loosened	Yes. One of the simpler repairs on the unit
An isolation or service valve	Valve packing or an internal seal has worn	Yes. Valve replacement
The pressure relief valve	Either a failed valve, or the valve doing its job because pressure is too high	Yes, but find out which. A relief valve discharging may be a symptom, not the fault
The heat exchanger body itself	The core component has corroded through	Usually not economic to repair. This is the warranty conversation
Water under the unit with no visible source, only while running	Often condensate drainage rather than a leak at all	Fix the drain line, not the heater

Find the source before deciding anything.

If it really is the heat exchanger

A heat exchanger is the core of the unit and the most expensive part in it. A pinhole in one is generally a corrosion failure, and corrosion does not happen in one isolated spot. Where there is one pinhole there is usually thinning elsewhere, which is why patching is not a real option and why a replacement exchanger on an older unit often approaches the cost of a new heater.

So the decision becomes: is it in warranty, and if so what does the warranty actually cover. Many manufacturers warrant the heat exchanger for a longer term than the other parts, and most of those warranties cover the part only, not the labor to fit it. Some require proof of annual maintenance or professional installation to remain valid.

What to gather before you call the manufacturer

The model and serial number from the data plate on the unit.
The original installation date and, if you have it, the installer’s invoice. Warranty terms frequently depend on professional installation.
Any records of descaling or annual service, because several manufacturers condition the warranty on maintenance.
Whether you are the original owner, since some warranty terms do not transfer with the house.

Why hard water matters more for these units here

A tankless heater runs water through a narrow heat exchanger and heats it very quickly. That is exactly the condition in which dissolved minerals come out of solution and deposit as scale. Las Vegas water is hard, so scale accumulates on the inside of the exchanger faster here than in a soft water market. Scale restricts flow, makes the unit work harder, and creates hot spots that accelerate corrosion. Descaling on a schedule is not optional maintenance on a tankless unit in this valley, it is what keeps the exchanger alive. See our tankless service and water treatment, because treating the incoming water is the thing that slows it down at the source.

If you are weighing replacement

Do not let a failure push you into a decision without a quote on both paths. Get the warranty answer first, then price a warranty exchanger fitted against a new unit. On a unit that is still young and was maintained, the warranty route usually wins. On an older unit that has never been descaled in hard water, a new heater may be the better value.

Talk to a licensed Las Vegas plumber

We find where the water is actually coming from before recommending anything, because most of the sources on that list are repairs rather than replacements. Kingdom Plumbing is family-owned, licensed, bonded and insured (NV Contractors License #0085422), available 24/7 with a real person answering and an upfront flat-rate quote you approve first. Call (702) 840-5037.

Frequently Asked Questions

Is a pinhole leak in a tankless water heater worth repairing?

It depends where it is. A leak at a fitting, an isolation valve, or the pressure relief valve is a normal repair. A pinhole in the heat exchanger itself usually is not worth repairing, because corrosion that produced one pinhole has generally thinned the metal elsewhere too. At that point it becomes a warranty question rather than a repair question.

Why is there water under my tankless water heater?

Check the condensate drain before assuming it is a leak. A condensing unit produces liquid water as a normal byproduct of extracting heat from the exhaust, and that water leaves through a small drain line. If the line is kinked, clogged, disconnected, or not sloping downward, the water ends up on the floor and looks exactly like a leaking heater. Water appearing only while the unit runs fits condensate.

Does the warranty cover a leaking heat exchanger?

Often, but read the specifics. Many manufacturers give the heat exchanger a longer warranty term than the rest of the unit, and most cover the part only rather than the labor to install it. Several also require that the unit was professionally installed and has documented annual maintenance. Gather the model and serial number, the installation date and any service records before you call.

Can hard water cause a tankless water heater to leak?

It contributes. A tankless unit heats water rapidly in a narrow passage, which is the ideal condition for dissolved minerals to deposit as scale. Scale restricts flow and creates hot spots that accelerate corrosion of the exchanger. In a hard water market like Las Vegas, descaling on a schedule is what keeps a tankless unit healthy, and treating the incoming water slows the buildup at the source.

My pressure relief valve is dripping. Is the heater broken?

Not necessarily, and this one is worth diagnosing rather than just replacing the valve. A relief valve discharges when pressure or temperature exceeds its setting, so it may be doing its job correctly and telling you something upstream is wrong, such as excessive supply pressure or a thermal expansion problem. Replacing a valve that was working correctly leaves the real issue in place.

How long should a tankless water heater last?

Manufacturers generally quote a longer service life than a tank heater, which is part of the appeal, but that figure assumes maintenance. In hard water, a unit that is never descaled will not reach it, because scale in the heat exchanger is the main thing that shortens their life. Annual descaling and treating the incoming water are what close the gap between the quoted life and the real one.

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