PostgreSQL pgpool-II replication mode doesn't work?
Postgres instances are normally replicated using Streaming replication which uses the WAL(Write Ahead Logs), which are transferred to secondary database to be replicated. So all incoming queries from application will go to the primary database and gets executed. These executions generate WALs which are then transferred to the secondary database and applied so that the secondary comes in sync with primary database.

As per pgpool documentation, the replication it uses is a statement based replication where the application connects to pgpool server instead of database(primary/secondary), and the incoming queries are then forwarded to database instances to be replicated. 

There are a lot of disadvantages of using pgpool replication setup. Functions like random(), CURRENT_TIMESTAMP, and sequences can have different values on different databases, also if the pgpool crashes, no query will execute, since the application is connected to pgpool, not the database.