Pull the stems and remove any tape you used.
The stems come with a round plastic seal.
All that tape will do, is lift the stem farther from the mating surface, and provide a place for water to leak past the seal.
Imagine someone putting their hand between the door and the doorjamb, you're going to get cold air in the house, right?
If you have replaced the "seats", those go in with a little pipe dope (thread sealant)