The 75 GPD Dow Filmtec membrane is the industry standard all others are compared against. When buying a unit from anyone no matter who it is the efficiency or rejection rate can vary by up to 15%, this is true of GE Water, Applied Membranes or anyone else. Its no secret and their data sheets are public knowledge, I have linked to them hundreds of times. The vendor may or may not replace it but it is not guaranteed. It is hit or miss and you get what you get. None of the vendors here is going to intentionally shortchange you but it happens. Imagine the failure rate with the cheap e-bay Chinese imports!
If you buy a Spectrapure unit with a Select series 100% individually hand tested RO membrane you get a guarantee that it is 98+% efficient and tested in their facility. You pay for this service but in most cases it is well worth the price difference in DI resin replacement savings alone.
All membranes regardless of manufacturer are good at some things and not as good at others, thats the nature of the beast, It all has to do with the physical size of the ions the substances contain. Thye are quite good at almost everything though and what they don't get is why you have a good vertical 20 oz DI cartridge on the tail end and prefferably a high quality 0.5 micron carbon block up front. It takes the whole combination to work well. particulate prefiltratrion, carbon adsorption, reverse osmosis and deionization.
