My ro is knackered and i need to by a new one but last sunday i filled up my van with my twin 27" di vessel the reading was 1ppm from them i have just filled up again as i am a bit behind this month so i have got to work saturday morning anyway the reading is still only 6ppm ok it is time to change but i have had 2400lt this week and my water is 240ppm .Makes me think how long would it last when i put new resin in ? .It would save me having a static tank in garage so more room and buying a new ro and all that wasted water i do fill bad about .