One homeowner's two-week hot-water saga proved frustrating after their tankless unit kept failing even after they installed a new gas valve, adjusted the gas pressure, and cleaned the filter.

Here's what to know

In a Reddit post, they said their tankless water heater first showed error code 11 and later stopped making hot water without displaying any code at all. 

"Not gas valve problem, not filter problem, not gas pressure problem…What could it be?" they wondered.

They called a plumber after not receiving hot water from the tap. The plumber installed a replacement gas valve and the hot water returned, but only for a day. 

The plumber was called in again, and they suspected that the gas pressure was too high. The homeowner called on their gas company to lower the pressure and add a new regulator. Again, the hot water returned, but only for a day. 

Their third attempt involved having the gas company raise the gas pressure, and again, their water was hot for only a day.

The homeowner then suspected a clogged filter was causing the issue, so they removed and cleaned it, but to no avail.

They said the problem had lasted roughly two weeks. "If anyone has similar experience please help…i've tried all the methods I've learned and still couldn't solve the hot water issue."

The original poster explained in the comments section, "The tank itself is on. It's just the flame [that's] being inconsistent. Lighting up for 2 seconds and [then] goes out then [lights] up again, goes out again." 

They added, "No error codes being observed in the past few days."

What can be done?

The issue grew into a bigger headache as the homeowner exhausted their options.

One commenter wrote, "Quit throwing parts at it and call the tech line, you'll need a multimeter and a manometer," while also advising the homeowner to find a plumber who knows those systems. 

But the recommendation fell short because, as another commenter explained, the tankless water heater company's warranty policy discourages many technicians from working on these systems.

The OP responded, "I've contacted the … tech line but they will only direct my call to the plumber companies they partnered with, and then the plumber companies wouldn't walk me through how to fix it without sending their plumbers here."

"I just had this issue and it was really hard to diagnose," another commenter added. "Long story short I had them order a flow control and I warrantied the motherboard for them. With both parts brand new it … wasn't working quite right. I found out the cable harness from the flow control to [the] motherboard had a connection that completely rotted out, which wouldn't allow the tankless to fire up. It essentially wasn't seeing water going [through] the unit."

"I have [an] update," the original poster wrote in response to this comment. "After cleaning the flaming rod and ignition, [it's] now giving code 11 again."

One commenter provided instructions for configuring the settings after the error code 11 reappeared. The OP responded, "I will try the computer setting you just sent! and if none of them worked [I] will [call] the plumber and have him help me."

Without finding the real cause, replacing parts over and over can become costly.

For homeowners who are tired of repeated service calls on gas equipment, Cala offers a different path. Cala's customizable smart heat pump water heaters can help homeowners decrease their energy bills by heating water exactly when it is needed. Those systems are built around more precise control of when hot water is produced, which can reduce wasted energy and trim monthly utility costs.

Upgrading to a heat pump water heater can sharply cut water-heating costs, with Energy Star estimating savings of about $550 a year for a family of four.

While switching does not solve this Redditor's immediate repair problem, it does highlight the longer-term choice many households face: whether to keep paying for diagnostics on aging gas hardware, or price out a replacement with smart features and lower operating costs from a company like Cala.

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