Hayward Skimmer Gasket Leak

Sp1085
I Removed Pavers And Excavated The Earth From Around One Of My Hayward Sp1085 Skimmers So I Could Remove It, Put It On A Bench And Replace The Piping Elbow Fitting On The Bottom. I Cleaned All Mating Surfaces And Reinstalled The Skimmer With A Pair Of New Gaskets. Guess What? The Gasket Leaks!!!! Should I Re-do It But This Time Put A Sealant On The Mating Surfaces? Pool Store Says No Sealant Is Required. Pool Is Inground With Plastic Walls And Vinyl Liner. If I Use Sealant, Such As Silicone For Glass Aquariums, I'm Sure The Stuff Will Be In Contact With Water Before It Cures. Do You Think That Will Affect It?