Can't agree Jim:
You are going in a whole new direction claiming 'Not Fit for Purpose'.
You must be loaded, because if you went to court to argue that you would lose....... heavily.
How is a carpet not fit for purpose ? by your definition because you say it can not be cleaned. (it can be)
The purpose of carpet is to cover the floor, add warmth, add to decor, trap soil, basically do what it says on the label.
The only way it would not be fit for purpose is if it had a manufacturing fault, was under specified by either the manufacturer or retailer (mis sold) or reacted in a adverse manner to a recommended cleaning procedure. Tough one this, as any manufacturer, should it go wrong, would argue that you did not clean it according to specifications.
This carpet was clearly fit for purpose and was not under specified, wool/flax will last for years in a high traffic area.
The method of cleaning for this carpet is LM or DRY, if you dry extract, it has been cleaned, therefore your argument goes right out the window, it can also be HOST cleaned quite safetly or with great care LM cleaned using pads.
In my opinion NO carpet is un-cleanable, its just up to you as a professional carpet cleaner to make a commercial decision as to whether you want to take it on or not, of course results would be dependent on the carpet and the process used which you qualify with the customer.
For instance why do we have so much trouble with Belguim Wiltons in this country ? it is because they are not designed to be fitted on underlay and gripper, in Europe they were/ are trade 100% stick down to hard floor, mainly in hotel environment, so when cleaned will not shrink,Its purely a British adaption to be fitted on underlay made by carpet buyers years ago who, saw an opportunity to sell 'Wiltons' very cheaply to low end users but they knew they would have to go on underlay and gripper in the home to give the appearance of a wilton installation.
Once they started shrinking after cleaning and they were inundated with claims for replacement due to under specification, they changed tack and changed the maintenance requirements covering themselves all end up and leaving poor old sud suckers picking up the bill.
Having said that T & C are a must and should be on the back of all your quotes and invoices.