Are you sure they are carpenter ants and not just regular sweet/piss ants?
Here is some info on Carpenter Ants and various treatments.
Sweet/Piss ants...I am swearing my life on Terro. TERRO ROCKS. If you don't like it, I will BUY it from you. Ants that love sweet things THRIVE on it...they flock to it....soak it up (and I've seen them do it)..and take it back to their nests which kills the rest of them.
Last week I used it upstairs and left the bottle on a table. The next day I went up and had all of these ants lodged up inside the cap trying to get in the bottle. It was soooo gross....but that is how well it works. Forget the powders, granuals, etc. Terro for stuff like that. And it is safe for humans/pets in low doses.
OH WAIT. I just read Carpenter Ants love sweet things, too....might give it a try!!!!! Seriously...I will buy it from you if you don't see a difference. Any would work, but we use the originalwww.terro.comhttp://www.terro.com/guide-ants.php
TERROÂ® Liquid Ant Bait is a sweet food based product similar to pancake
syrup combined with Borax. Borax is a mineral that is mined in the desert
in California and is a common active ingredient that is used in soap
products such as 20 Mule Team Borax.The product kills ants but will not harm people or pets.
If you spill some
on your skin there will be no reaction at all. Simply wash with warm water.
Pets occasionally find the Terro and eat it. Our advice when this happens
is to do nothing at all. The product is not toxic enough to cause a problem
and the pet will be just fine.