A paint cup assembly for a paint sprayer can include a cap formed with an external rim and a plurality of threads adjacent to the external rim and a paint reservoir configured to engage the cap. The paint reservoir can include a distal end formed with a hub having threads configured to engage the threads on the cap. Moreover, a seal can be disposed between the external rim of the cap and the distal end of the paint reservoir. The seal can be compressed between the external rim of the cap and the distal end of the paint reservoir as the paint reservoir is threaded around the cap. Further, the seal can prevent air infiltration into the paint reservoir as paint is withdrawn from the paint reservoir by a spray gun.
