DEAR SAM: Recently, you were kind enough to solve a problem for me with garage doors; now I am hoping you'll help me again. Everytime I turn off the running water at any faucet, I hear a lound banging noise and pipes vibrating in the house. Could you advise me how to correct this problem? - S.J.A., Hasbrouck Heights, N.J.

ANSWER: Your trouble is known as water-hammer, which results when the directional flow of water in the pipes is suddenly stopped. During the construction of a house, air chambers, consisting of short sections of pipe (about 12 inches) are vertically set above each faucet line and capped. When the water is turned on, there is little or no water in these air chambers; however, during a quick turn-off, there is a "back-lash" of water entering the empty, capped section which serves as an air cushion.

Unless you do not have these air chambers installed, it is possible to restore the air cushions by releasing any excessive accumulation of water which impedes their correct operation. It is achieved by cutting off the water pressure in the system. You can do-it-yourself, as follows (1) Close the shut-off valve below each toilet tank. (2) Close the main gate valve after the water meter, usually located near the basement foundation. (3) Open the faucets of all fixtures, in the top floor, first floor and basement, such as laundry tray, to allow complete water drainage from the piping. (4) Now close all the faucets, open the main gate valve and toilet tank valves. The water system should be now under its normal water pressure. (5) Open each faucet and you will notice some sputtering and possibly some discoloration of water, both of which will subside as the air escapes. (6) Test the effectiveness of the air chambers by closing each faucet quickly to determine whether water-hammer has been eliminated.

If the problem has not been resoved, either because no air chambers were originally installed to take care of water hammer or because a few were omitted or have become defective, you will need a master air chamber in your system, which is easily installed by a plumber after the main gate valve and meter in the basement.

DEAR SAM: My son, who is an excellent carpenter, would one day like to go into business, such as refurbishing old homes (100 years or so) with woodwork, window frames, heavy doors, etc. that are unable to be purchased regularly. Are there any books, magazines, photographs, etc. on the subject? Thanks a million. - Mrs. D.C.S., Ambler, Pa.

ANSWER: The library should have several books on Colonial homes. Architect Royal Barry Wills' publication should be quite helpful. The "Architectural Forum," although it may not be available at all libraries, some old editions may still be around at major libraries.

Concerning woodwork materials, mahogany, walnut and other hardwoods were quite common in usage, not only for panels but for general finish, doors and even windows. It would be quite expensive to duplicate them during these zimes. For your son to develop a profitable business, he should undertake such refurbishments only under contract for a specific buyer or owner.

Sam Fishlyn welcomes your letters on home improvements but only those of general interest can appear within the limited space. Write to him at P.O. Box 62, Newton Centre, Mass. 02159.