Example aspects of an outer housing for a pressure monitoring system and a pressure monitoring system for a wet barrel hydrant are disclosed. The outer housing for a pressure monitoring system can comprise a sidewall shell defining an axis extending centrally therethrough and comprising an annular inner sidewall projection extending from a top end thereof; and a cap mounted to the sidewall shell, the cap defining an annular cap recess, wherein the annular inner sidewall projection is configured to engage the annular cap recess.