Oh man, I just re-read your earlier post where you say your post RO is 0.5EC. This filter lifetime in your case would only be 18,750gallons/250PPM (0.5EC) = 75 Gallons. So it is not going to work for you, it would work in the case where your post RO is lower. In your case a softener is the best like other people have suggested and then maybe you might need a DI as well. A softener will make your RO filters last longer too. Don't want you wasting your cash on a DI when the filter is only good for 75 gallons in your case. Don't want to be spending 70$ every 75 gallons.