The square nut in front of the pump body leaks; what is wrong and how do I fix it?
The square nut in front of the pump body is an air inlet valve that allows air into the top of the pump cylinder during dry flush operation to stop any Vacuum kick. Inside the square fitting is a check valve. In units manufactured between 1981 and March, 1992, a small black joker valve was used; in units manufactured after March 1992; a more advanced valve is used. In either case, remove the fitting and rinse it with warm, clear water. Reassemble. If it still leaks, replace it (part # 1203W).
