Hi Jerry
Opinions on this vary a little, but in general, you don't use a disclaimer form. It would prove to be worthless anyway if you were found to be negligent.
The way many of us work is to carry out a full audit on every job. If you find a fault eg. split seams, pre-shrunk carpet, loose dye etc. you simply write on your survey form that "Pre-cleaning inspection has revealed....."and add that cleaning may further damage this pre-existing condition. I will then write: Permission to procede with works given by A.N. Other and they sign this.
Safe and happy cleaning
The Ken