pgadmin3 incredibly slow over network

If I use pgAdmin3 to query a remote database with SELECT * FROM big_table, the whole thing takes 1.5 minutes until I get my results.

If I run the same query, from the same computer, to the same remote database, using a different client (HeidiSQL, or even pgsql), it takes 5 seconds.

I run pgAdmin 1.22.2 on Windows 10, and the postgreSQL database is on Linux. The postgreSQL version is 9.3, but it doesn't seem to be specific to the

version. The same happens on 9.4. The large performance differences happen in other queries as well, to various degrees of difference.

What could be causing this?