PostgreSQL pg_dump output reading from named pipe on Windows is giving duplicate dump content

PostgreSQL Version - 9.2.8

Dump command : pg_dump.exe -U postgres -Fc -b test

Platform : Windows Server 2008 R2

Output of dump command is redirected to write end of named pipe. From read
end of the pipe data is read. From 'strings dump-file' output I could see
that all the SQL statements in the dump file are repeated.
Also I see below errors in dump output.

*pg_dump: [custom archiver] WARNING: ftell mismatch with expected position
-- ftell used*

This doesn't happen if the pg_dump (on Windows) is redirected into a file
or '-f outputFile' option is used.

Please find attached dump file ( test-WithPipe.dump ) and strings output of
dump file ( test-withPipe.dump.strings)

Why do we see this behavior with pg_dump command using PIPEs ?

*test-withPipe.dump.strings*

CREATE DATABASE test WITH TEMPLATE = template0 ENCODING = 'UTF8' LC_COLLATE
= 'English_India.1252' LC_CTYPE = 'English_India.1252';
DROP DATABASE test;
postgres
false
-----------------
-------------------------
-----------------------------
CREATE DATABASE test WITH TEMPLATE = template0 ENCODING = 'UTF8' LC_COLLATE
= 'English_India.1252' LC_CTYPE = 'English_India.1252';
DROP DATABASE test;
postgres
false
2615
------------
--------------------------------------

Thanks
Girish