fax machine & ADSL

I have an existing phone line, and it's dedicated to the dsl. the thing is, my dad wants to buy a fax machine and use the dsl phone line to the fax.

of course, i'm thinking that if the line can be split (using a splitter) to dsl and a phone, it can be done to the fax too.

or would that be something bad? I need your views/suggestions, /comp/. thanks.