Ants in the house can be regular old house sweet ants or carpenter ants. You can see the difference. If your ants go after food lying around the house they are sweet ants. But those that avoid regular food to get to some water; they may be carpenter ants and are tough to eliminate.
Carpenter ants use the plumbing vent stack as an expressway from the basement to the attic. (They share it with the mice.) There is damp wood available in the attic behind the gutters or in the rotting roof boards that are replaced when a house is re-roofed. They also have damp wood available under a bathtub due to worn out caulking or a faucet leak. Sometimes a little sawdust on the floor around the stink pipe in the basement can indicate infestation of carpenter ants.
For regular house sweet ants, I recommend using Terro ant. It is syrup containing borax, not poison, applied to cardboard scraps that the ants carry back to the nest. Usually it wipes out the whole colony in about three days. This product is not recommended for carpenter ants, but works great for sweet eating ants.
Getting rid of carpenter ants can be very difficult. The main reason is you have to locate the nest in order to eliminate the queen ant.
If you do not eliminate the queen ant, she will take some eggs, a few workers, and run to safety. She will then establish a new nest in some damp lumber elsewhere. It could be years before you see another carpenter ant. If you do not remove the queen, you will only be hiding the problem.
Enforcer Products makes Cypermethrin, available at most hardware and garden centers for about $10. It is a concentrate that produces about two gallons. That should be more than sufficient to eliminate a colony of carpenter ants as long as you get the queen. Eliminating the ants is not the only thing you have to do. You also have to rid your house of all the potential homes for the ants. If they do not have food and habitat, they will not stop and visit. Places to check for ants are; leaks in the plumbing, in and under windowsills, wood behind gutters (especially after ice dams), and outside woodpiles.