After the owner of a new house saw daylight around their tankless water heater's ventilation pipe, they took to social media to uncover how dangerous the setup was.
Here's what to know
The resident took their issue to Reddit's r/homeowners forum, writing: "Builder says this is acceptable. Am I crazy to think that it is not?"
The original poster shared an image of the setup and added: "The pipe should be properly fitted into the hole. Also, light visibly passes through from the outside during the day."

Fellow homeowners challenged the builder's reassurance about the opening.
"I'm assuming gas exhaust, so if you see daylight and it is not sealed, this would be a carbon monoxide concern as well as pests and draft," the top commenter said. "100% this must be sealed up. This can't be up to code."
Another user wrote, "I don't think it's right, but unless it gets blocked, there isn't a carbon monoxide danger."
A third commenter added: "Not crazy at all. I'd take photos from inside and outside with the light showing through and email them to the builder so there's a written record, not just a verbal 'it's fine.' New builds usually have a warranty walkthrough, so get it on that list."
The user also recommended: "Pull up the installation manual for your model. They usually spell out how the vent penetration has to be sealed, and quoting the manufacturer back to the builder tends to work better than arguing." If the builder refused to address the issue, the commenter advised asking the city's building department whether the final inspection had included a review of the vent penetration.
For homeowners considering a different water-heating system, upgrading to a heat pump water heater may help lower energy bills. If you're exploring replacement equipment, Cala offers smart heat pump water heaters. Cala's customizable smart heat pump water heaters can help homeowners decrease their energy bills by heating water exactly when it is needed.
Where can I learn more?
Water heater venting problems have led to inspections, warnings, and equipment shutdowns in other homes.
• A Texas inspector found a new-build vent flaw that could spill carbon monoxide into the attic.
• A home inspection flagged water heater backdrafting, and plumbers warned repairs could be expensive.
• A renter spotted odd water heater exhaust before a carbon monoxide alarm started beeping.
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