Roofing/oily residue runoff from asphalt shingles
QUESTION: We just had a new three tab asphalt shingle roof installed, after a severe hail storm in south texas. About a month after the roof installation, we had a very light rain shower and I noticed a puddle on the driveway that had a rusty brown oily residue film on top. After the water evaporated, it left a brown stain on my driveway. Two weeks later we had a big thunderstorm. I collected the rain coming down off the roof in a clean bucket and transferred it to a clear plastic bottle. The water was the color of dark brown tea. Is it normal for a brand new roof to have this type of runoff? Could it be defective shingles? Who would be able to insure quality shingle material was used on my roof?
Based on your description, the brown water is runoff from rusted flashing. Very likely your chimney flashing.
When it rains, the water that touches your chimney flashing beccomes stained with the rust and that's why it turns brown.
This tells me the roofers did not replace your chimney flashing, It could also be rusted drip edge or step flashing but more likely the chimney flashing.
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QUESTION: Your answer is very valid, but in our case, the side of the roof in question has only two valley's and nothing else. It does not even have any of those vent pipes that stick out from the roof. The roof shingles over-hang some from the side of the house, so I do not believe it could have been from a drip edge or flashing. The contractor stated they no longer use that piece of metal where the valley's end. The only other thing they added was ice & water shield on the eaves and valleys. I am not even sure what that consisted of. There is nothing rusty on the roof that could have produced water the color of dark tea.
Are the valleys you mentioned open? This means that they have a metal W-valley flashing that can get rusty and cause this dark rusty color.
Was the flashing replaced when you had the roof replaced? Are the shingles stained with the dark brown color?