How do you remove an airlock from the bathroom water heater?

When you say air lock what do you mean? Also when you say bathroom water heater are you talking about and under sink water heater or a 6+ gallon water heater. In my experence water heaters don't tend to air lock. The waret heater is designed to eather push air through it into your pipes or it will travel back into the water main. Generally you can assume that air in a perssurised sysetm will travel the path of least resestance. That does not mean that a pipe cannot air lock when the pressure on one end is equal to the pressure on the other.  more