I have seriously got to stop delaying the inevitable and start upgrading from the 100 GPD I am using to make water asap. I started a thread a few months ago about pure freedom 950 gpd high volume reverse osmosis and later decided against it. Truth is I am having a hard time understanding the different between 4040 reverse osmosis kit, 4021 reverse osmosis kit and 600gpd RO system. I can't ring these people up who sell the stuff to ask Q's I need to know. I guessing 600 gpd ro is already very similar to what I already got but without booster. WHAT I do know is I want to be able to make 500lt of water at my parent place in the back garden ideally take no longer than 6 hours to make in the day (cos my parent don't like leaving the tap running at night) and transfer the water to the van. Also which make the most water in a short space of time without the booster? I am in hard water area with tap reading of 384.