UNPROTECTED GAS FLUE VENTS ON ROOF, SEE PHOTOS

[Gene South]

From today’s inspection. One builder was building every home in the neighborhood. In all homes except the one I happened to be inspecting had conventional metal furnace flue vents. The house I inspected had schedule 40 PVC flue vents however on the roof, the PVC flues had no way to prevent rain water from entering the top of the flues. From the roof, the furnace flues appeared to be plumbing wet vent stacks. This local area had approximately ½ inch of rain in the past 24 hours. Both HVAC condensate pans contained about one inch of water and water inside the cabinet. The outside temperate was around 40 degrees so the units were in heat mode, not cooling mode so there was no condensate from AC operation.
FLUE VENTS.jpg.IMG_8344.JPGIMG_8550.JPGIMG_8342.JPG

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[Jerry Peck]

In all homes except the one I happened to be inspecting had conventional metal furnace flue vents. The house I inspected had schedule 40 PVC flue vents ...

Possible that your house had higher efficiency heater and the vent was condensing the water to the PVC vent, which then (naturally) ran back down (due to gravity) and out the bottom of the vent?

If so, there should be a method to collect that condensate and drain it off to a place of disposal.

[Vern Heiler]

From today’s inspection. One builder was building every home in the neighborhood. In all homes except the one I happened to be inspecting had conventional metal furnace flue vents. The house I inspected had schedule 40 PVC flue vents however on the roof, the PVC flues had no way to prevent rain water from entering the top of the flues. From the roof, the furnace flues appeared to be plumbing wet vent stacks. This local area had approximately ½ inch of rain in the past 24 hours. Both HVAC condensate pans contained about one inch of water and water inside the cabinet. The outside temperate was around 40 degrees so the units were in heat mode, not cooling mode so there was no condensate from AC operation.
FLUE VENTS.jpg.IMG_8344.JPGIMG_8550.JPGIMG_8342.JPG

1/2 inch of rain is only about 1/2 cup of water into the vent. While a scupper would have prevented that 1/2 cup from entering the furnace, I don't think the rain water is the real problem. The furnace condensate drain should be able to handle much more water than that. I think the traps built into the furnace or drain lines from the fan housing are clogged.

One other possibility is that the condensate drains are connected in the furnace vertical configuration rather than horizontal.

[Gary Burnett]

Billy Stephens posted this back in 2007.
Might be of help. It shows that the vent stacks are proper at the roof.

- - - Updated - - -

Billy Stephens posted this back in 2007.
Might be of help. It shows that the vent stacks are proper at the roof.

[Vern Heiler]

Billy Stephens posted this back in 2007.
Might be of help. It shows that the vent stacks are proper at the roof.

- - - Updated - - -

Billy Stephens posted this back in 2007.
Might be of help. It shows that the vent stacks are proper at the roof.

Installation instructions are for a up-flow furnace which is not designed for horizontal installation. You must use the installation instructions for the furnace in the O.P. It should show two different condensate drain ports, one for vertical and one for horizontal.