Using the wrong copper tube could lead to watery disaster

Q. I always read your column in the Sunday newspaper, and wanted some more detail to your answer to an earlier question. I have had similar problems with the cold water pipe that runs to my hot water heater. Would you be able to further clarify the possible causes?

A. Below is an expanded explanation provided by another reader following my answer to the initial question about a strange green deposit on a horizontal section of copper pipe above his water heater.

My answer was that a small hole or a porous area had developed over time, and that it could have been caused by acidic water or a thinner wall section in the pipe at that particular point.

"Plumber's copper tubing comes in Types K, L and M. Type K is the thickest and is designed to be used in underground service, such as the utility feed from the street to the house. Type L is mid-thickness and is designed for continually new water service, such as inside distribution. Type M is the thinnest and is designed for the continuous re-circulation of the same water, such as hydronic heating. Since the average user doesn't know this, and they are each interchangeable with standard fittings, they grab the cheapest tube from the shelf for their project (including new construction).

"Water conditioning, as you mentioned, will help a bit, but is not sufficient. The root problem is that copper, like almost every other metal, will dissolve in water. Type K, since it is underground, is dissolved from the inside out, and outside in. Type L is only dissolved from the inside. Type M will only be dissolved until it reaches its saturation point in the captive water, then it will stop.

"Homeowners can check to see if they are destined for this problem by closely looking at the tubing. If they can see a faint red stripe along the tube, this indicates Type M. If it is blue, indicating Type L, they will be all right for a much longer time."

My thanks to this reader, who provided this clear and thorough explanation of the possible causes. There is a lot of knowledge among the readers of my column, and I appreciate all the help I get from them.

Q. I noted your advice in an earlier column not to use a power washer on vinyl siding when using a certain product, Oxy-Boost. Is that advice specific to that product, or would you not use a power washer on vinyl siding at all? Thank you for your assistance.

A. The advice to not use a pressure washer on vinyl siding is not specific to Oxy-Boost.

As stated in the answer to the question you are referring to, it is difficult to find a pressure washer with low enough pressure to avoid damaging the siding.

An electric pressure washer (which typically has lower water pressure than a gas-powered washer) kept at a safe distance from the siding might work, but you are always taking a risk.

The safer ways to wash vinyl siding are with a rotating car wash brush attachment to a garden hose (these brushes usually have a detergent cup) or a soft-bristle hand brush dipped in a bucket of detergent and water.

Q. Can you tell me why carpeting gets dark along baseboards? It is especially noticeable with light-colored carpeting. My house is only 10 years old and we are the original homeowners. What can I do about it?

A. I assume the stains are along the baseboards of exterior walls. Dark stains along these walls are an indication of outside air infiltration. It sounds as if no sill sealer was installed under the outside walls during construction.

If that is the case, the carpet can be pulled up and caulking applied where the bottom plate of the walls rests on the floor. If it is possible, it is best to do this repair from the outside.

Interesting suggestion from a reader: "There was a letter written in today's paper by someone with stains from a bath mat left in the tub too long. I've personally removed rust stains from an old sink with ketchup. I read somewhere that this works and it did! I just spread it on and let it sit, and it sure worked. Don't know if this would work on the black stains, but I don't think it would hurt to try."

Oh! The power of tomatoes!

Q. My husband was recently diagnosed with a lung disease, and as a result we had our air quality tested and a mold inspection. Luckily, the air quality in the living quarters is fine, but the mold inspector discovered a lot of mold in our attic.

I believe the mold is the result of either adding additional insulation in 2010 or a problem with the installation of the roof in 2004. I know that the mold was not there when we purchased the house in 1998, as we had a good home inspector.

Our house has a mansard roof, and the "upright" parts of the mansard are not open to the top roof. The top roof has a relatively shallow pitch. We have a solar-powered attic fan and five square mushroom-type vents on the back of the house.

Today, we had an attic ventilation specialist out. He was well recommended on Angie's List and by the mold inspector. He could not determine the cause of our ventilation problem, but said adding additional vents or replacing the solar fan with an electric-powered fan might help. Our bathroom fans are vented out the roof separately.

Tomorrow, the mold remediation contractor will be out. I hesitate to remediate the mold without understanding and fixing the cause, or we will be in this situation again. I know you mention that air moves from the soffit vents out the ridge vent. My husband says we do not have a ridge vent. Since mansard roofs do not have a soffit, where would the air enter?

Also, we know that when the wind is right and it storms very hard (about once a year), we get water in our foyer. We have had roofing companies out to try to determine the source, but they have been unable to find it. I mention this only because it might be related.

I took the attached photos from the ground. If I need to do so, I will get up on the garage roof to take a close-up of the "edge" where the roof meets the upright section of the mansard. Any ideas?

A. My best wishes for your husband's prompt recovery. Mold develops in attics from one or more reasons. They can be:

• Bathroom and/or kitchen vents discharging into the attic.

• A defective venting system for the bathroom or kitchen, with holes or poor joints in the ducts, disconnected joints, a waterlogged loop, etc.

• Convection of warm, moist air from the conditioned space into the attic.

• Roof leaks.

• Absence of a vapor retarder protecting fibrous insulation.

• Other unknown or undiagnosed surprises in a field fraught with potential construction errors.

In a difficult situation presented by a mansard roof, construction should be such that air can circulate from the lower roof's soffits into the upper roof, and out a ridge vent.

The better choice is to insulate with closed-cell polyurethane to create what is known as a hot roof, the insulation itself being an effective vapor retarder.

I can't tell you if the added insulation or new roof is responsible for the problem without considerably more details on what was there before and what was done at those times.

You have not said if the mold found is only on the lower roof or also on the upper, flatter roof. The upper attic ventilation system is unusual and, if mold was found there, it shows how ineffective it is.

The attic ventilation specialist has not been very helpful, and I doubt his suggestions to improve the situation will do much.

It is also unfortunate that the bathroom fans are vented through the roof. It is never a good idea to do this in cold climates, as condensation runs down and may wet the insulation, damage the ceiling and cause the fan to rust. These fans should be vented through gable walls.

Looking at the photo of the front of your house, I would suspect the foyer leak is coming from either the flashing at the connection of the window above the foyer to the roof itself or where the canopy protecting the front door connects to the main roof. An experienced roofer, general contractor, home inspector or engineer should be able to figure it out.

After mold remediation, you may want to consider replacing all the insulation with closed-cell polyurethane and removing all roof perforations. It will be simpler than trying to insert ventilation in both roof planes.

Q. Can you recommend the best approach to cleaning rust off my aluminum flagpole?

A. Try rubbing the pole with Zud, available in the cleaning-supply aisle of supermarkets or in hardware stores.

• Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. His book, "About the House," is available at www.upperaccess.com. His website is www.henridemarne.com. Email questions to henridemarne@gmavt.net, or mail First Aid for the Ailing House, Universal Uclick, 1130 Walnut St., Kansas City, MO 64106.

© 2016, United Feature Syndicate Inc.