Is my power vent water heater flue safe?

Old 05-26-18, 07:27 AM
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Is my power vent water heater flue safe?

My house has a power vent water heater, and I'm concerned about the little yellow vinyl cap on the coupling (between the vent fan and PVC flue) in this picture:

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If I pull the cap off when the water heater is running exhaust gas comes out. Three people have seen this and not been particularly bothered by it (installer, home inspector, furnace guy) but this still gives me the willies. It seems like all that stands between me and flue gas (carbon monoxide) is this press-on vinyl cap. Is this really ok, and if not what's the correct way to seal off this port?

As a side note, for some reason the flue for the water heater (which is PVC all the way) runs all the way up through the roof of the house, rather than out the basement wall like the furnace intake/exhaust.
Old 05-26-18, 09:42 AM
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That's a test port. Very low pressure in the exhaust so it's extremely unlikely that cap would pop off. They make rubber caps with clamps or you can put a small worm drive clamp on there. Just slightly tighten it.

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