the fittigns with the o-rings never use pipe tape on them. they are designed to be sealed with only the o-ring. pipe tape if its on too thick may stop it from seating correctly and giving an improper torque reading. also in terms of sealing the taper part of the fitting, you need to make sure that the fitting are parallel when being isntalled. also make sure you are meeting the minimum bend radius requirements of the hose. a 3/8 stainless hose is about 6" minimum bend.