This fits your .

This Pentek 153070 #20 Big Blue housing sump fits caps for Pentek #20 Big Blue filter housings with any inlet and outlet size, and same size housing caps made by several other manufacturers. It is made of reinforced polypropylene for strength and resistance to chemicals. This sump meets National Sanitation Foundation/American National Standards Institute (NSF/ANSI) standard 42 for quality assurance, and is for use with Pentek #20 Big Blue housings , which are used in various applications, including residential drinking water filtration, food service, and humidifying systems, among others

Pentek 153070#20 Big Blue Housing Sump (Pack of 4) - B07FJNTPZY