Here you go:
Go to the page of your pipe, for example: http://pipes.yahoo.com/pipes/pipe.info?_id=99240a186b2099bc028d7d7e37c1f224
Click on the Get as RSS link, for example: http://pipes.yahoo.com/pipes/pipe.run?_id=99240a186b2099bc028d7d7e37c1f224&_render=rss
Edit the URL, change the
render=rss
torender=csv
, for example: http://pipes.yahoo.com/pipes/pipe.run?_id=99240a186b2099bc028d7d7e37c1f224&_render=csv