Q: Every time we turn on the hot water in our new house the pipes bang. The plumber says the banging does no harm since it is only the pipes expanding and hitting the wood structure. What do you say? The house is guaranteed until November this year. Isabella E. Welsch Lincroft, N.J. A: If the pipes expand and hit the wood, then ask the plumber to tie them down so they can't make all that racket.
On the other hand, the banging of the pipes may be caused by what is called an ''air hammer,'' a condition triggered when the faucet is suddenly shut off and the rushing water bangs against the valve.
This condition is not hard to cure if you have air-hammer arresters installed ahead of the faucets. Such gadgets cushion the shock of a sudden cessation of rushing water against a column of air in the pipe, which thwarts the banging.
As to the relationship between the banging in the pipes during the guarantee period, the plumber may or may not be responsible, depending on the wording in the plumbing specifications.
Do they call for air-hammer arresters? If not, then you may have to pay for their installation.
In my book, however, the plumber, at his own expense, ought to snug the pipes to the structure so they cannot expand, if indeed this is the cause of the noise.