A:AnswerNo, it is recommended to use this unit with warm water only. However, for use with Epsom salts, you can use HoMedics model FB-65-THP or FB-350 Compact Pro Spa.
A:AnswerI would say probably not. I put a 12" ruler in the foot area, and it leaves just a little room if you wanted to move your foot up and down a little. a 13" foot seems like it would fit flatly, but there wouldn't be any room to move the foot except sideways a little bit.