I used this combined with the tech wash on an old pair of snowpants that had almost literally turned into a sponge, they had no water repellency whatsoever. The water beaded up nicely after the treatment, but it wasnt completely water proof. Water would start to soak through a bit if it was left pooled up in an area, i.e. your dirty snow encrusted butt... so by itself its not going to be 100%. I used the spray on stuff after the fact and now its pretty much made of plastic, aint no water getting through there.
I see this as more of a "maintenance" product for keeping gear that still has some waterproofing working great.. just dont expect it to make a completely non-waterproof fabric function 100%