A common trap with many airless paint spray pumps is leaving pressure in the pump system after use and forgetting that the airless spray pump still retains pressurized paint or cleaning liquid. Always open pressure bypass prime spray valves fully before switching off or leaving the machine unattended.
It can be all too easy for someone to pick up the airless spray gun, thinking that because it is not on that it will be safe to pull the trigger, not realizing that there is still residual pressure remaining in the airless spray pump system. It could be possible with many piston airless paint sprayers that the unit is still even on and has simply stalled at the point of maximum pressure setting.
The very least that can happen after an airless spray gun trigger is pulled in a case such as this is a mess with paint or fluid sprayed everywhere, but it can be much worse with risk of injection injury or liquid sprayed into someones eyes from the residual pressure remaining in the airless paint hose and pump.
Airless Spray Pressure Releasing
Consult the owners manual for your model to locate and follow the manufacturers recommendations for operating the airless and recommended pressure relief procedures that should be followed. Many manufacturers incorporate over pressurisation relief capability into the bypass valves on pumps these days to protect the equipment and operators.
Older airless spray units may not have had a bypass valve fitted as standard and with a valve pressure relief can only be achieved via the spray gun. Some units may have been retrofitted with a ball valve to act as a bypass valve but the ball valve should be capable of handling the pressure.
Take care to secure any paint bypass hose when pressure relieving an airless spray pump as the pressure and flow can cause the hose to recoil which can be enough to force it out of the container.
Typical Airless Spray Bypass Valve
Remember to always completely open the prime spray bypass valve on airless sprayers.