Big Blue filter housings offer the versatility to meet all of your large-capacity filtration needs, including high-flow and heavy-sediment applications. The extra large housing allows for greater cartridge capacity, reducing the number of vessels required for high flow-rate applications. Sumps are constructed of durable reinforced polypropylene. The high-flow polypropylene (HFPP) cap is available with 3/4", 1" or 1-1/2" FPT inlet and outlet ports. The 1-1/4" internal port allows a greater volume of liquid to pass through the HFPP cap more rapidly. Big Blue housings are compatible with a broad range of chemicals and come with a pressure relief button. They accept a wide variety of 4-1/2" diameter cartridges.