Piston airless spray painting pumps use seals of some type to maintain paint pressure and stop paint from leaking. The most common seals used in airless spray paint pumps are V packings.
V packings in an airless pump are stacked in opposite directions at either end of the piston but which direction is the correct way to install packings?
The point of the V must point out of the pump or away from the paint/pressure side. The V packings are compressed between the piston and the cylinder usually by some type of packing nut and as pressure is exerted against the opening of the V packings the edges are forced against the cylinder and piston with greater force.
If the V packings are inserted around the wrong way with the point of the V pointing into the pump, towards pressure the packings can easily collapse away from the piston and cylinder allowing paint to leak and pressure to escape.
One of the most common V packing materials used in paint pumps is a combination of Teflon and leather V packings. It is usually recommended to soak the leather V packings in some type of oil similar to normal motor oil to impregnate the leather before installation. Coating Teflon and leather packings with a light smear of grease will assist in installation of new packings into an airless piston pump. Simply flush the airless pump with turpentine to clear any grease from the paint side of the pump prior to the first job after a pump repack.