why do i keep getting an air lock in my hot water sysyem?

every two or three weeks I turn on the hot water but find there is an air lock in the main closed hot water coil from the boiler to the hot water tank.I have to open the pipe and let the air lock out
Why do I keep getting an air lock in the system
There is no signs of any water leaks
Mr Tom park, January 2005


done
Yeah its because ure a bender

Smokeefe, June 2007