Try cinnamon around the ants point of entry to the house, and sprinkle it around the perimeter of the house several times a year.
I had an ant super high way several years ago, and sprinkled cinnamon on it. Within 2 hours the ants had abandoned that highway! I think cinnamon interferes with the ants sense of smell and destroys their ability to follow the trail left by the scout ant - the one who found the "gold mine". If directly poured on them, it kills them.
I sprinkled it under the outside of the door jams, and repeat that every year, and have had no more ants in the house.
There is no guarantee that this will work - your ants may be different from the ants here in SC - but it's cheap to try. If you could make some kind of a paste with the cinnamon, you might be able to "paint" it on the pipes or in the tiles.
WARNING: I don't recommend using this on fire ants because they are so aggressive, and may not be affected by cinnamon! I've never tried cinnamon on them because of that.