Tony, I was taking the pee. You know there are many variables, Whats the carpet pile made of, has the customer scrubbed it to death, what cocktail of goodies have they used?
To tackle it you need to remove as much of the contaminent as possible, try using plain cold water first. Feceas contains old blood
hence the colour and cold water is the best way to remove it.
Once you've done that see what you are left with. Any major staining then treat with an enzyme based pre-spray. Allow the dwell time stated for the product to work, then extract off.
You may still be left with a stain. You could then try rust remover or something like red rx.
The colloid type products are also quite good on these types of stain.
Finish with a decent de-odouriser.
Qualify with customer first that stain may be permanent.
Jason's just answered the question as well.