I literally bought an apec water systems RO system off of Amazon and I’m getting consistently between 1-3 ppm. I’m using well water going into a salt softener system, then through a big blue 3 stage filter system, and finally a uv sterilizer, that is what feeds my house. I just took a line off of that to feed the RO system, and it’s awesome. So awesome in fact, I had to double my 4x8 tent to an 8x8 tent mid grow. Lol. My 12 plants are drinking about 4-5 gallons a day. I have a bluelab monitor, and my ph hasn’t gone above 6.3 or below 5.7 ever, since switching to RO with the ph perfect nutes.