While he's watching TV in the next room, Bob Dobson can sometimes hear the new water filtration system by his kitchen sink trickling for hours. 

It's a sound he finds irritating, and an uncomfortable reminder of the nearly $8,000 contract he signed last November with Atlantic Environmental Systems, a Dartmouth, N.S.-based water purification company.

He deeply regrets entering the contract which he says he signed after a sales presentation at his home in Halifax that lasted roughly three hours and…