That pipe you are describing is a T&P valve relief line.
If it is leaking after the heating cycles are complete or more towards the evening/night hours when no one is using hot water, then you have a issue with thermal expansion.
There is a chance that the T&P valve could be defective and replacement is economical but most times it can be caused by thermal expansion.
Let us know what your water pressure is in the area either by gauging a hose faucet outside with no water on in the house.
These gauges can be found at all big box stores/hardware stores. Here’s a picture of what you need:
Also, let us know if you have one of these where your main shutoff is:
Or one of these at your water heater:
DUNBAR
Website Moderator
» This message has been edited by DUNBAR on 21 April 2006