Step 1:
Install the S.S. Spring into the Red Cap, then insert the HEX of the red cap into the pocket.
Step 2:
Make sure the O-ring seat is clean and free of nicks and scratches.
Optional: You can lubricate the O-Ring with a silicone lube approved for potable water.
Step 3:
Install the O-Ring onto the S.S. Self-Tapping Pan Head Screw and insert through the hole and thread it into the Red Cap.
Never use petroleum-based products, like Vaseline. Petroleum can cause elastomer rubber to swell of dry out.
Solvents are not ideal lubricants and contain high volatile organic compounds (VOCs) that may be flammable or pose very real health risks. Soap and water solutions are safer than solvents and petroleum-based lubricants, but are nominal, inconsistent, and reactivated in wet or damp environments after assembly.
Additional Resources:
https://support.boshart.com/water-is-dripping-from-the-red-button-on-my-water-filter
https://support.boshart.com/how-can-i-remove-a-water-filter-bowl-that-is-stuck
https://support.boshart.com/how-to-replace-a-whole-house-water-filter-cartridge
https://support.boshart.com/how-do-i-identify-what-filter-cartridge-i-have-in-my-water-filter
https://support.boshart.com/how-often-should-i-replace-the-filter-bowl-on-my-sediment-filter
https://support.boshart.com/how-do-i-identify-what-filter-cartridge-i-have-in-my-water-filter