Although silicones with PEG in front of them are supposed to be water-soluble, I have not really trusted this promise because my experience with DevaCurl OneCondition seemed to leave me with some buildup. So, I've been avoiding all 'cones, including the ones with PEG before them.
But today, someone posted at naturallycurly.com that there is a difference in solubility among the PEG 'cones. Here is what the poster (who claims to have majored in chemistry in college) said:
As far as pegylated dimethicone - yes, some of them are water soluble. Anything with less than 4 is not at all. Anything 4-6 is very slightly water soluble. Anything 6-8 is moderately water soluble. 8-10 have good (but not great) solubility in water. 10+ are completely water soluble. the "PEG" part is polyethylene glycol - a very water-soluble side chain. The longer the side chain, the more willing these 'cones are to "work" with water. It's my understanding that things with fewer than 10 are prone to buildup without sulfates.
So, this gives me a little more confidence to at least look for higher numbers when considering a product with a PEG 'cone. Good info!