The system really quite smart. It will store the filtered water into the pressurised tank. And stop once the tank it fills up. no, its does not "waste" any water, a RO system uses water to clean itself and wash away impurities. It's like a lot of other water-using appliances. We use water to wash clothes, to wash dishes, to wash cars, to flush toilets. A reverse osmosis unit uses more water in its operation than you actually consume,yes. but it doesn't use enough that you'll notice it on your water bill. It uses water only while it's filling its storage tank. When the tank is full, the whole unit shuts down and no water runs to drain. In terms of expense, it's like a couple or three extra toilet flushes a day. it will be even less if you do not use the water for washing but just drinking. I think the APEC is really value even after shipping. A 3M 5stage filter cost 2.3k to buy and install. Even hyflux does not provide 5 stage RO filter and it cost already 1.xxk for 3 stage