I hope someone can offer some advice on a problem that has perplexed me for some time. I have knocking water pipes. I'm familiar with water hammer and its causes, none of which apply in my case. Furthermore, the pipes aren't loose. The knocking seems to occur close to where the water line enters the house (basement). Now the mystery is this: it happens almost exclusively in the early morning hours, say from 4-6 a.m. I can turn on any faucet for a few seconds and it stops. Any suggestions would be much appreciated.