Bleeder style spray guns have a continuous flow of air through the air cap when the HVLP turbine is “on”. Bleeder spray guns are the original style HVLP spray gun supplied with Apollo turbine spray systems. They are simple in design, extremely reliable, and easy to clean and maintain. Some people are under the misconception that the continuous air flow will displace dust and dirt in the spray area and workshop. In fact, it will not, in any way affect the performance. The fallacy originated when HVLP manufacturers began offering non-bleeder style HVLP spray guns and circulated inaccurate information in order to promote the alternative non-bleeder concept. HVLP manufacturers continue to successfully offer bleeder style spray guns.
Non-Bleeder HVLP spray guns do not bleed air when the HVLP turbine is “on” until the trigger on the spray gun is pulled back. These style guns operate more like traditional compressed air spray guns. When the trigger is pulled, the first stage releases the air, and the second stage releases the material into the air stream. Non-bleeder spray guns are slightly more complex than bleeder style HVLP spray guns and require a turbine system to have some form of air relief to prevent back pressure to the motor. This air relief may be internal or external. Apollo only uses external bleed ports on their turbines as this is the best way to push the hot air outside the turbine box and not amplify the heat inside the box.
Other than the cost, there is no advantage or disadvantage to using a non-bleeder HVLP spray gun. It is a matter of preference and/or choice. Generally, HVLP bleeder spray guns are less expensive than non-bleeder HVLP spray guns. When using an older turbine system without back pressure relief built into the turbine, non-bleed spray guns may still be used, but an external air relief must be installed. Apollo makes an air relief that can be installed on most brands of turbines, which will allow the operator to use a non-bleed spray gun without damaging the turbine motor.