Sep. 27--Q We have a plastic outdoor play set for our children that they've outgrown. How do we get rid of it? Can it be recycled?

A No, it can't be recycled. It can be re-used, however. If it's still in good condition, consider selling it at a garage sale, on craigslist.com or eBay.com. You can give it away at Twin Cities Free Market (www.twin citiesfreemarket.org).

Return and replace

Q I purchased and installed an on-demand gas water heater when they were fairly new to the market. The only model that Home Depot carried at the time turns out to be rated only to minus-4 degrees. That means whenever it gets colder than that, the air coming back through the direct vent freezes the water in the reservoir. This stops the flow of water through the water heater unless I let the hot water tap run continuously. To get the water running again, I have to remove the cover plate and thaw the reservoir with a blow dryer. What can be done? Are there any after-market fixes, such as a heater, that will correct for this problem?

A Return the item to Home Depot, because it's obviously something that will not work in this climate, said state energy specialist Phil Smith.

The Twin Cities has design conditions of minus-16 degrees. The warmest location in the state has design conditions of minus-11 degrees. The sale of a device not intended to work in our cold climate is an error on their part.

Adding a heater to this device, or any other after-market solution, would void the UL listing and create a potentially dangerous condition. You need to replace this device.

Discolored roof

Q My six-year-old roof is discolored on the north side of the house and garage and under mature trees. It doesn't wash off with a garden hose. Do you know what it is, how to get rid of it and how to prevent it?

A It sounds like a fungus or algae. A north-facing roof under overhanging tree branches is ideal for such growth: damp, shady conditions that stay relatively cool and dark.

To solve the problem, you'll have to alter those conditions or regularly remove the growth.

--Trimming the trees will let in more light and air.

--Add copper or zinc strips to the roof ridge and under shingles at intervals down the slope. Metal inhibits the growth of algae and moss, and as rain falls, it will pick up minute amounts of metal, washing it down the roof. Or install algae-resistant asphalt shingles.

--Try removing the growth yourself. Start with an application of half-chlorine bleach and half-water and apply at the rate of 1 gallon per 30 to 50 square feet. Wear protective glasses, gloves and clothes. Attach plastic garbage bags to the ends of downspouts to keep the runoff from killing grass and plants. Cover foundation plants. Finish by rinsing the gutters with clear water to prevent corrosion. The solution will kill algae immediately, but it may take several days for the black discoloration to disappear. If it doesn't, repeat with a stronger solution.

--Consider hiring a contractor to clean the roof.

Send your questions to Fixit in care of the Star Tribune, 425 Portland Av., Minneapolis, MN 55488, or call 612-673-7032, or e-mail fixit@startribune.com. Past columns are available at www.startribune.com/fixit. Sorry, Fixit cannot supply individual replies. Fixit appears daily except on Fridays.

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