I've been using an Envirodri E40 for about 5 years. Before that it was many years with a Host T6. IMO, the weight of the Envirodri is beneficial.
Pile damage? None for me. I use predominantley the softest Gold brushes. Superb job. The standard white, or often even the Chipmunk, are too agressive for wool and many nylons and could cause pile burst and excessive shedding. The white brush is great on cut pile polyprops for opening the flattened pile and removing a little more fibrous soiling. Use this for commercial loop nylons and polyprops.
Never use the stiff blacks on any polyprop. I only use them on Flotex, both dry and wet. Superb.
Like many other users, I initially had a mind set that the stiffer the brush, the better the cleaning side of the job. WRONG
The softest brush will usually perform all the pile lifting you want in a safe way, and the aforementioned JB likens the solution distribution of soft brushes as being more like applying paint with a paintbrush as opposed to trying to do it with a stiff scrubbing brush. Much better job. Regardless of the explanation, soft brushes work best.
I clean many wool carpets every year and have not seen any signs of premature wear due to my agitation methods.
With the Envirodri and the Host, you can work with the handle from both sides of the machine. The last Prochem Fibredri machine I used was probably a nicer, quieter performer (but not better), but you could only work from one side of the machine, and not with the handle vertical either. Also, Prochem more expensive than Envirodri, but cheaper than Host.
Although rarely seen, the Host T6 replacement (Reliant?) without an attached vac, is probably still available.
Safe and happy cleaning
Ken
PS I may know of a lightly used E40 for about £400.
