Navien Tankless Water Heater Repair in Buckeye, AZ: What We Found Behind One Verrado Install

A homeowner in the Verrado area of Buckeye called us to look over their tankless water heater. Nothing was flooding. The unit ran — mostly — but the hot water had never quite lived up to the promise on the box, and they wanted a second set of eyes on the install. By the end of the walkthrough, Donnie had a list.

The heater itself was a good one: a 199,000 BTU Navien, a workhorse of on-demand hot water. But it was being fed through a gas line rated for less than half its appetite. Its acidic condensate drain was tied into a safety line where it never belongs. The recirculation loop had no expansion tank and no check valve. The house had no defense against some of the hardest municipal water in the Phoenix metro. And the whole home was limping along on 30 PSI of water pressure. None of it was one big mistake. It was a stack of small ones, the kind we see all the time on tankless retrofits, and every one of them was fixable.

Here's what we found, why each one matters, and what we did about it.

The signs your tankless water heater needs a repair visit

If any of these sound familiar, your install deserves a look:

• Showers that run weak, or fade whenever a second fixture opens
• Hot water that cuts out mid-shower or swings between hot and lukewarm
• Error codes on the display — on Naviens, E011 and E012 often trace back to the gas supply
• White mineral crust on fixtures, or a unit that needs descaling more than once a year
• Chalky streaks running down the exterior stucco below a small drain line
• Ticking or banging pipes after the water heater fires

Every one of those symptoms showed up in this job's findings. Here they are, one at a time.

What we found in Verrado — and why it matters to your house

The gas line: feeding a 199,000-BTU heater through a straw

This Navien can call for 199,000 BTUs the moment someone opens a hot tap. The flex connector feeding it was rated for 85,000 — the yellow corrugated kind that's perfectly fine on a furnace or a tank-style heater, which is exactly why it ends up on so many tankless retrofits. On a unit this size, that line becomes a straw.

The burner calls for fuel, the line can't deliver, and the heater runs lean: incomplete combustion, flame dropouts, and soot slowly coating the burner assembly. On Navien units, that's the story behind many E011 and E012 error codes, and it's one of the first things we check when a tankless water heater isn't working. The unit doesn't fail all at once. It runs starved, wears out early, and makes hot water you can't count on.

A condensate drain tied into the safety line

Every high-efficiency tankless produces acidic condensate — typically pH 3 to 5 — as a byproduct of combustion. At this house, that acid drain was piped straight into the copper line serving the temperature-and-pressure (T&P) relief valve. That valve has one job: open and discharge water if pressure or temperature ever climbs to unsafe levels.

Tying an acid drain into it creates two problems, and neither one announces itself. The acid slowly eats the copper from the inside — that's how you get pinhole leaks hidden in a wall. And debris or backpressure in the shared line can keep the relief valve from opening in the one moment it has to. Plumbing code requires condensate to run separately, in corrosion-resistant pipe like PVC, to an approved drain point. Here it was also terminating above the stucco, and those chalky streaks aren't just cosmetic. The acid etches the finish.

A recirculation loop with no protection

This home has a recirculation loop — the setup that keeps hot water moving so the far bathroom doesn't wait a minute for a warm tap. It's a great feature. But heated water expands, and in a closed loop with a backflow preventer at the meter, that expansion has nowhere to go.

Without an expansion tank to absorb it and a check valve to keep flow moving one direction, every heating cycle sends a pressure spike through the pipes: hammering fixture seals, joints, solenoid valves, and the heat exchanger itself. You hear it as ticking or banging. Your plumbing feels it as wear.

Hard water with no defense

Municipal water in Buckeye and the surrounding West Valley typically measures very hard — roughly 180 to 250+ ppm of dissolved calcium and magnesium, or 11 to 15+ grains per gallon. Inside a tankless heat exchanger, that mineral load bakes onto hot metal as scale, insulating the surface, forcing longer burns, and eventually cracking the exchanger. In our experience, an unprotected tankless in this water gives up years of its design life.

30 PSI of water pressure

Our gauge read 30 PSI at the hose bib. The comfortable range for a home — and what a multi-fixture tankless is designed around — is 40 to 60. At 30, the shower feels tired and two fixtures can't run at once. Low city-supply pressure isn't rare on the west side, and we see the opposite problem too: here's a pressure regulator repair in Verrado where the house had far too much. Either direction, pressure problems shorten the life of everything downstream.

How we diagnosed it

No guesswork. A gauge on the exterior spigot came first: 30 PSI. Then the BTU rating on the Navien's data plate against the flex line's rating and the standard fuel-gas sizing tables: 199,000 BTU of demand on an 85,000 BTU line. Donnie traced the T&P and condensate runs by hand to the stucco termination, tested the water for grain hardness (GPG) and total dissolved solids, and checked the recirculation loop for an expansion tank and check valve. Neither was there. One inspection, six findings, all documented before we talked about a single fix.

What we did, step by step

1. Hard-piped the gas line. Out with the undersized flex connector; in with rigid black iron pipe and a full-port 3/4-inch gas shutoff valve, sized to the appliance instead of the other way around. This is standard gas line repair and re-piping work for us, and it's the difference between a burner that runs lean and one that runs at full, clean fire with steady temperatures.
2. Gave the safety line its job back. We decoupled the acid drain, repaired the copper T&P line, and re-routed it to stand alone the way code draws it. Your relief valve can now open the moment it needs to — that's the whole point. Then we ran a dedicated PVC condensate line out through the wall, terminating at ground level over gravel. Off the stucco for good.
3. Protected the recirculation loop. A factory-required 3/4-inch check valve keeps flow one-directional, and a 2.1-gallon thermal expansion tank (6-year manufacturer warranty), mounted on its own bracket, gives expanding water somewhere to go. The pressure spikes stop, and the ticking stops with them.
4. Treated the water. We installed an Encore Reveal whole-home water treatment system to remove calcium, magnesium, chlorine, and heavy metals before they reach the heat exchanger. No minerals, no scale. No scale, no early replacement.
5. Boosted the pressure. A Grundfos SCALA2 variable-speed booster pump now monitors the house continuously and adjusts its motor speed to hold pressure steady in the recommended range, whether one tap is open or four. It's quiet enough that the only place you notice it is the shower — in the good way.

The work, at a glance

Component	What we did
Gas supply line	Replaced the undersized flex line; hard-piped with a 3/4" full-port ball valve for the full 199,000 BTU demand
Condensate drain	Separated from the T&P line; ran a dedicated PVC drain to exterior ground level, away from the stucco
T&P relief line	Restored an independent copper safety line, routed to code
Recirculation loop	Installed a 3/4" directional check valve and a 2.1-gallon thermal expansion tank (6-year warranty)
Water quality	Installed an Encore Reveal whole-home treatment system to stop scale at the heat exchanger
Water pressure	Installed a Grundfos SCALA2 variable-speed booster to correct the 30 PSI city supply

The result

The same Navien, now fed and protected the way its engineers assumed it would be: full fuel at full fire, a relief valve with a clear line, a loop that can breathe, treated water through the exchanger, and steady pressure at every fixture. The install finally matches the appliance.

When to call a professional

Gas sizing, combustion, and relief-valve work isn't DIY territory — it's exactly where a licensed plumbing contractor earns their keep, and where an improper install can put a manufacturer's warranty at risk. If your system's symptoms match anything above, our water heater repair services cover tank and tankless alike, and the diagnosis starts with exactly the checks you just read about.

Tankless water heater FAQ for Buckeye homeowners

What size gas line does a 199,000 BTU tankless water heater need?

Big enough to deliver its full rated input over the actual run length — which the fuel-gas sizing tables translate to 3/4-inch or larger hard pipe in most homes. Many yellow flex connectors are rated around 85,000 BTUs, less than half of what a 199,000 BTU Navien can draw. Feed a tankless through one and it runs fuel-starved: error codes, flame dropouts, and early wear.

Why does my Navien tankless water heater keep shutting off?

The most common causes we find around Buckeye are fuel starvation from an undersized gas line, scale from our hard water, and low water pressure or flow. Navien's E011 and E012 codes point to ignition and flame failures, and those trace back to the gas supply more often than most homeowners expect. A real diagnosis checks fuel, water, and venting before anyone replaces parts.

Do I need a water softener with a tankless water heater in Arizona?

In the West Valley, we strongly recommend one. Water in Buckeye commonly measures 11 to 15+ grains per gallon — very hard — and that mineral load bakes onto a tankless heat exchanger as scale, cutting efficiency and shortening its life. Manufacturers publish hardness limits, and running above them can affect warranty coverage. Whole-home treatment removes the minerals before they ever reach the unit.

Can a tankless condensate drain tie into the T&P relief line?

No. Tankless condensate is acidic (typically pH 3 to 5), and plumbing code requires it to run separately in corrosion-resistant pipe, like PVC, to an approved drain point. Tied into a copper T&P line, the acid corrodes the pipe from the inside, and debris can block the relief valve — the one component in the system that must never be blocked.

Is 30 PSI water pressure too low for a house?

Yes. The comfortable range for a home is 40 to 60 PSI, and multi-fixture tankless performance assumes it. At 30 PSI, showers run weak and two fixtures struggle to run at once. When the city supply itself is low — which we do see in parts of Buckeye — a variable-speed booster pump like the Grundfos SCALA2 holds the whole house at steady pressure.