I don't know about this, but I do recommend a really good CHEAP as chips way to do it by hand....
I used to have a carpet cleaner machine, but now I do it lilke this:
Never use soap.
1 bucket of really really hot water and about 1/2 cup of household ammonia or bicarbonate of soda. Pretreat any stains first with some Vanish stain remover just like you would clothes.
Then take a scrubbing brush, the stiffer the better and get down and scrub that carpet until it is all clean.
Then get another bucket of hot hot water and a terry towelling cloth. RIng out the cloth really tightly and then just 'rinse' all over until the whole carpet is wiped over and rinsed, continually rinsing out and ringing out the cloth also of course. Leave to dry completely before walking on it. You can use an old toothbrush for the the edges. it is also more motivating to keep it clean as it was such an accomplishment to clean it.
And as always, always colour test an inconspicuous place first.
good luck