Can I cut vent pipe?

I have a 16' rise, so I had to buy a 20' pipe (3 inch diameter).

Then the woman who sold it to me said "No! You can't cut it...you'll void the warranty."

What the hell? Am I supposed to make wiggly 's' bends in the chimney until I use up the extra four feet?

Yep, the corrugated spiral type.

Thanks for the prompt replies!

Edit: this is a Quad 1200i in a masonry firebox.

That's what I thought, thanks guys.

This is a Quad dealer in Santa Clara, CA. The gal working in the office isn't the best resource for technical info...so glad I found this forum!

ironpony said:

I cant believe all you experts missed the obvious answer.
let the four feet stick out the top of the chimney......................

Click to expand...

I like it! Maybe once I'm running, the stack will flip and flop all over the place, you know, like one of those blower-driven inflatable advertising balloon guys. The tire shop always has one dancing around on the corner during tire sales!

But seriously, I have plenty of metal fab equipment in the garage...cutting it won't be a problem. But I will post pics when I'm done, I'm sure you guys will critique it.

Right now, I'm just planning to run the 3" flex past the damper and to the top, capping it off with flashing and a termination cap. I'd sure like to see some pics of finished off chimney tops. Does this forum have a gallery??