Halting electrolysis in water pipes, fixing a leaky chimney

Q. Our 18-year-old residential copper water lines are troubled by electrolysis. The water appears to be dissolving the copper in the pipes, thus staining the tub and basins a bluish-green. Some pipes have pinholes, and leak. We've tried a number of solutions, such as a dielectric union, and have even separated the electrical system and grounded the water lines to an outside copper stake that is driven into the ground. Even so, the problem persists. What is the answer? Philip J. Roe Buena Vista, Colo.

For those who don't know about electrolysis, the problem results in disintegration at the connection between the copper and iron pipes. An electrolytic fitting between dissimilar metals thwarts the reaction.

Ask an experienced commercial water-softening firm to test the water to determine its mineral content and recommend a water conditioner to remove the offending minerals. That done, the bluish-green discoloration should disappear.

The mechanical device that softens the water will also clean out the pipes, but at the same time it may produce some leaks. Wherever leaks occur, you will have to replace the pipes.

Q. Our house has an open-beam ceiling, a roof pitch of 3 inches in 12, and a large, used-brick chimney piercing it. Reflashing of the chimney and replacing bricks above the flashing have not prevented leaks. The roofer says the flashing should be recaulked every couple of years. I think the counterflashing should be installed with the top embedded in the masonry so that periodic caulking is unnecessary. Someone recommends a steel chimney pan with the edges folded down over the brick one course above where the counterflashing is embedded. Should we tear down the top of the chimney and start over again?

Bruce H. Morgan Annapolis, Md.

Do you have a ''cricket'' on the back/high side of the chimney? A cricket is a small, false canted roof designed to throw off water from behind the chimney.

Metal flashing and counterflashing wherever the roof meets the chimney walls is a normal requirement. All flashing should be adequately bent, lapped, and sealed with a resilient caulking compound equal to polysulfide, butyl, or silicone rubber. The sealant needs regular maintenance. The upper counterflashing is let in and caulked at slits, usually in the mortar joints just above the roofline. Each metal flashing lap is a potential leaker, especially if the sealant has dried and cracked.

At this distance, I see no reason to tear down the chimney merely to place, replace, or caulk new or old flashing or counterflashing. Check the horizontal joint between the last and the next-to-last flue tile atop the chimney, and seal it if necessary. Another likely place for leaks is the poured cap atop the chimney. There the flue liner should extend 2 or 3 inches above the concrete cap. The cap should slope down and away from the flue to positively drain the rainwater. Check the joint between the flue liner and the poured cap. Heat expanding and contracting the flue may develop a crack between it and the poured cap. Caulk it! Replace the concrete cap if it is cracked or has a reverse pitch.

In a freeze/thaw climate, avoid applying a silicone sealer to the outside face of the chimney, since such sealing may trap moisture inside the brickwork.

The Brick Institute of America's technical notes No. 19B, revised as of June 1980, discusses a prefabricated chimney cap in preference to a poured-in-place cap, metal rain caps, and preferred sealants. The institute's address is 1750 Old Meadow Road, McLean, Va. 22101. The phone number is (703) 893-4010.