A liner for containing a soaking solution in use with a foot spa features two bodies of plastic which are joined at an interface therebetween so as to form two, individual layers. An air conduit is formed between the two layers so as to provide a passageway for pressurized air, which is supplied by an air discharge apparatus, across walls of the liner and into the soaking solution. The inner layer has openings such that the air guided through the air conduit can be released into an inside volume of the liner where the soaking solution is containable. Furthermore, the outer layer is imperforate from a location thereon at which a starting end of the air conduit is disposed to a free end of the layers so as to isolate the inside volume of the liner from the soaking basin.