I have a Rowenta also, it leaks. it has since the day I got it. I also use tap water. I find that it must be hHOT HOT HOT, I mean, have it on for 5 minutes or so before I use it or it will leak. I also never fill it to the top line, I usually use it half way.
I paid about $100 for my iron, it was not worth the money.