Q: I have gutters and downspouts from the upper roof of my two-story home that drop water down onto a lower roof. The lower roof drains...

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I have gutters and downspouts from the upper roof of my two-story home that drop water down onto a lower roof. The lower roof drains this water down into the gutter below. It seems like this increased water flow on the lower roof would cause much more wear there. Why don’t the downspout pipes continue from one gutter to the next?

Downspout lines are not extended across the roof simply because they are not attractive. When you have a long run from one gutter to the next, a large pipe running down the roof is a hideous sight. Furthermore, a pipe on the roof is subject to damage from people stepping on it or tree limbs falling on it, and it is more prone to plugging (as is the gutter).

More importantly, a downspout running down the roof would have to be secured to the roof. That would mean putting nail or screw holes into the roofing. Every hole is a potential leak point.

There are ways to attach this pipe without holes through the roof, but the cost is prohibitive. Thus, another reason you will not see continuous downspouts.

All that said, you raise an important issue about roof wear.

Roofing materials, particularly in composition roofs, are subject to greater wear beneath drains. Sometimes that extra wear requires replacement of a small roof section before the remaining roof fails.

Leaks inside walls are more likely if step-flashing isn’t installed correctly — where upper walls meet lower roofs on a pitch. Ever see water screaming out of a second-floor downspout, onto the lower roof and right off the edge laterally? This happens a lot because the roof overhang always has a slight outward tilt.

Do I have a better solution? Nope. Like everything else, it is a trade-off and ultimately a function of the design of the building.

Displaced stove part causes carbon-monoxide leak

My sister called last Sunday and told me the fire department was just driving away. That gets someone’s attention real quick, I can tell you. She called 911 when the carbon-monoxide alarm went off while she was cooking dinner, accompanied by a strong smell.

The firefighters took carbon-monoxide readings throughout the house with the windows open and found the highest levels near the gas stove. As a precaution, the firefighters shut off the gas and told them to sleep upstairs with the windows open.

The next day I went over to check things out. When I looked at the integral gas cook top, I saw that one of the burner diffusers was cockeyed but still in its holder. It was caked with black soot on the back side.

Gas combustion does not result in black soot production unless there is a serious problem with the burner or something blocking the flame (called flame impingement). Flame impingement happens frequently on gas fireplaces when the ceramic logs are too close to the burner — causing that black soot stain up the side of the log. It also happens on furnaces with filthy burners.

Flame impingement causes incomplete combustion, and carbon monoxide. Because gas stoves are not vented to the outdoors, she got a high CO reading. I adjusted the diffuser, and the problem was solved.

Diffusers typically look like miniature round tables with several little legs — kind of like those plastics gizmos pizza places use to keep the box lid from touching the cheese. They need to sit in their cradle precisely, but they can be knocked out of place when the stove is cleaned. As is often the case, it’s the little things that matter.

Darrell Hay is a local home inspector and manages several rental properties. He answers reader questions. Call 206-464-8514 to record your question, or e-mail dhay@seattletimes.com. Sorry, no personal replies. More columns at www.seattletimes.com/columnists.