Can a rotten potato remove floor stain?

Q. I read your column every week. I have a 37-year-old vinyl linoleum in my large kitchen. It is discolored and white and gray with a green and yellow pattern in every other block. I would like to strip it down to the original whiter finish. One day I discovered that a potato from a bag that sat in the corner had gone bad. When I picked it up, the floor was stripped of the discoloring and looked great. Do you know what "acid?" the decaying potato produced. Was it oxalic acid? Do you know what I could use to resurface the floor like this other than using decaying potatoes? One cannot find any decorative vinyl floor covering anymore! So I don't want to replace it.

A. What a discovery! If a rotten potato did such a great job, I'd stick to rotten potatoes. Hard to handle, but what success!

Potatoes contain several acids, including amino, oxalic, salicylic, ascorbic, phosphoric, phenolic, etc., but it would be difficult to determine which one, or a combination of them, is responsible for removing the discoloration.

Probably the easiest and best cleaner is ammonia in water. You'll need a lot of ventilation.

You can also try CLR or TSP-PF.

Q. I own a house in Vermont that has a flat rolled rubber roof and a hatch leading to the roof from the inside. Recently part of the hatch cover (top of the "box") broke and a pre-existing leak around the hatch became worse. I was wondering if you had a recommendation for roofing repair companies in the area.

Additionally, we have a drain on the roof that leads to a drywell. The drain opening is round and approximately 2 inches in diameter. It is covered by a flat metal piece with holes. Over that I have placed a series of strainers to further prevent large pieces of detritus from plugging the flat strainer. Invariably it still gets plugged by accumulating silt/dirt, etc. Any solutions to this problem, such as a fan below in the pipe? The drywell works as it should when the strainer is not clogged. Can drywells be cleaned out the same way septic tanks can?

A. This is a busy time of year for most contractors trying to get things done before winter makes it difficult or impossible.

Any roofing or general contractor experienced in rubber roofing installation should be able to fix the hatch. The question is: Will anyone with that experience be able to fit a small job in?

The roof drain is quite small and I wonder where is the drywell servicing it? Is it accessible?

I don't know of any way to keep debris from clogging the drain cover other than getting on the roof as needed to clear any accumulation of silt and tree junk. You have tried several stainers without success.

I am not sure what you mean by a "fan below in the pipe." I don't know of any fan that would fit in a 2-inch pipe, and if there is such a thing, how would it be installed, how would power be supplied, how effective at blowing stuff clogging the drain cover, and would it survive repeated wettings.

If by cleaning the drywell the same way as septic systems, are you thinking about pumping the drywell? If the drywell is functioning properly, there should not be standing water in it; water should be absorbed through the bottom of the well and its sides.

Drywells can eventually silt up and become useless unless the silt can be removed.

Q. We just had our bathroom remodeled. The contractor left black grout specks on our white marble tile floor. Any idea on how to get rid of this residue?

A. If the grout is very young, try wetting it by laying wet paper towels over it to soften the grout. Then try scraping the specks off with a hardwood stick or a Scotch-Brite nylon pad. If the grout is epoxy, it will be near impossible to remove it after it has hardened.

Q. Thank you for your informative column. I have not written before and thought of you as I am struggling with a furnace replacement decision, which brand/model to consider. Our current gas boiler was the original installed in 1992. It heats by way of water baseboard heat. It is a Slant Fin boiler and we've been pleased with it. We've only had a few problems over the years. This year the relays all needed replacing and we realize it's just a matter of time so we're interested in replacing the boiler. We have a plumber whom we trust recommending a Weil McLean gas boiler to replace our current one. The plumber says they're easy to install and easy to repair. We have a four-zone home (three levels of living space and the hot water tank). The square footage of each floor is 1,100 and about 800 living space in basement, total 3,000 to heat. The reviews on the Weil McLean look mixed, especially for cold weather areas. Also the reviews mention difficulty getting and waiting times for parts needed for repairs. Our hot water tank will also be replaced at the same time. We contacted our gas company, which also provides repairs for gas furnaces, and asked for a recommendation or note of those they repair frequently and they could not give us any thoughts about brands to avoid, or to recommend.

We don't have any contacts who have had to replace a furnace so we're not sure what brand to look at. Do you have a recommendation for gas boiler and hot water tank?

A. Most brands of furnaces and boilers will have good and not-so-good reviews.

The main thing is to have a reputable and trusted contractor to do the installation and servicing when it becomes necessary. You are fortunate to have such a contractor, and you may want to follow his or her advice.

But you may also want to ask him or her if they can install a Buderus boiler, which has a good track record.

Additional information: In last week's column, I suggested to a reader asking about replacing a water heater that if he has an electric heater, he might want to replace it with a Marathon plastic tank because they last a very long time.

I neglected to add that Marathon plastic water heaters must be installed by HVAC contractors experienced in their installation because it is easy to damage the plastic connections to copper if not done with special care.

This from a reader: "I read your Sept. 17 article from a reader who has a backup sump pump in her crawl space. She wonders if there is a better way to ensure that it works in the event of a power outage.

There is an alternative, water-powered emergency backup sump pump. If she does not have well-supplied water, which requires electricity to operate the pump that brings the water to her house, this could work.

Here is a link to one that Home Depot sells. AquaPro Submersible Water-Powered Emergency Backup Sump Pump-35034-5 - The Home Depot."

I looked it up and this is what the manufacturer claims: "Uses municipal water pressure to protect your basement in case of a power outage. This pump provides added piece (sic) of mind. It helps remove unwanted water before damaging overflow occurs. No electricity needed. Home water pressure is harnessed to create suction draining power. Compact design fits alongside primary sump pump in basins 10 in. or larger." The cost is listed as $105. I have no experience with this product.

• Henri de Marne, a former remodeling contractor turned columnist and consultant, is the author of "About the House with Henri de Marne" (Upper Access Publishing). He continues to take questions from readers for this column and his website, www.henridemarne.com. Email questions to aboutthehouse@gmavt.net.