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Homebuyer finds corroded water heater vent — $500 repair may not prevent $3,500 replacement

The city's search found no permits filed from January 2020 onward.

A close-up of a plumbing joint showing corrosion and residue around the pipes and fittings.

Photo Credit: Reddit

A home inspection left a buyer with a potentially costly question: Could the water heater's corroded power vent be repaired, or would the heater need replacing?

Here's what to know

The buyer asked Reddit's r/Plumbing community whether replacing the power vent, as a plumber had advised, would solve the problem. They said the water heater had been replaced in 2021.

"Why change out the heater itself? Do you expect the condensate damaged it?" the OP asked after a commenter recommended replacing the entire unit.

One user put the potential costs at $500 for a replacement motor or $3,500 for a new heater. They blamed the corrosion on condensation running down the venting and warned that the moisture could reach the burner assembly.

Beyond the immediate repair bill, buyers facing a replacement also have future energy costs to consider. Heat pump water heaters move heat into water rather than generating heat directly, reducing the energy needed for hot showers and other daily uses.

More background

One user questioned whether the flue sloped away from the heater. Another said a drain at the blower coupling could be necessary for long vent runs or routes through a chimney or an unconditioned space.

One user suggested having a plumber explore a warranty claim, noting that six-year coverage on a heater installed in 2021 would run through 2027.

The buyer questioned whether the previous owner had installed the heater themselves after checking the installation's paper trail with the city. The city's search found no permits filed from January 2020 onward.

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What can be done?

One user recommended replacing the blower motor and connecting a drain rather than following others' advice to replace the heater.

Determining which approach would address the problem could help the buyer decide what to request from the seller before they took responsibility for the equipment.

If replacement becomes necessary, Cala offers configurable smart heat pump water heaters. Their water-heating schedules can be matched to household demand, helping reduce energy use and bills while keeping hot water ready when it is needed. For a buyer weighing equipment costs alongside future operating expenses, that scheduling flexibility is a feature to consider when comparing Cala units with replacement options.

The buyer sought more information by leaving a message with the seller's plumber, weighing those costs against the possibility of losing the home.

"We might end up just eating the replacement cost. My wife really doesn't want to blow up the deal over this, but it's still good to understand what we're walking into," the OP said.

Where can I learn more?

Other homeowners have also sought advice about damaged water heater vents and whether replacement was necessary.

• A plumber challenged replacement advice after a homeowner reported a rusted-out water heater flue.

• A homeowner's question about duct tape on a flue drew warnings about deadly combustion gases.

• After chimney work, professionals warned that furnace and water heater venting could send exhaust the wrong way.

• A warranty helpline flagged gas water heater venting after a homeowner's two-year-old unit repeatedly shut off.

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