mcp6453 wrote:

My home was built with Qwest PB pipe. When it failed, the company paid
to have my house replumbed in copper. Since then, whenever we turn on
the hot water spigot, particularly in the bathrooms, there is a small
burst of air. There are no plumbing leaks. Someone told me that there is
a cannister of some sort in the line that elinates the problem, and that
the cannister is bad, but I cannot remember what it is. Can someone
explain the source of the problem?

May have been thinking of a thermal expansion tank:
http://www.zurn.com/pages/catalog.as...OperationID=11
Look at Model HXT.

Mineral conditions inside the water heater may be producing
small amounts of gas (not air) which rises to the top of the tank.
I'm not sure that an exp tank will solve that.

If your water source is a well, I would suspect gases produced
from interaction with the magnesium anode rod.

Offhand I can't see a connection to the piping replacement.

Jim