Although, I don't know if you can buy this spot lifter because I can't find it any where. It works just like the sub surface carpet extractors I use when cleaning penetrating spots out of carpet. I clean carpets professionally in Tampa FL and I run into carpet problems that have gone way past the carpet on a daily basis. Spills on carpet can quickly penetrate all the flooring layers in your home, including: the carpet backing, carpet pad, and the sub flooring underneath. The only way to treat penetrating carpet spots is to rinse and extract all layers of the flooring.
The biggest culprit for this type of staining is pet urine. When your pet urinates on the carpet without you know it seeps into the sub floor and crystalizes. Those urine crystals off gas ammonia producing that all so familiar urine smell. You can clean the carpet all day long but if it's not neutralized in those sub layers beneath the carpet your problem is not going away. Spot vac looks like a lot of the other professional grade tools that I use on a daily basis here in Tampa FL. I can't seem to find a place for a consumer to buy this particular tool. I think it is still in the production phase and it has not been put to market. I hope it makes it because it's the correct way to remove tough carpet spots and stains that keep coming back.