A disposable valve assembly configured for use with an endoscope is disclosed. The disposable valve assembly may include a stem comprised of thermoplastic material, a spring stanchion configured to receive the stem and allow movement of the stem in an upward and downward position relative to the spring stanchion, a spring configured to contact that spring stanchion and the stem. In some embodiments, a lubricant is disposed on the stem, the spring stanchion and/or the spring. The disposable valve assembly may also include an antimicrobial agent disposed in the lubricant, or in the thermoplastic material and/or can be coated thereon. A method for manufacturing the disposable valve assemblies for use with an endoscope may include several steps.