I don't know if many have done this but I hear about pumps to pump water out of tanks or water butts. Today my water butt was full up with rainwater reading 011tds. I connected a hose to the tap and connected the other end of the hose to my di unit. My di unit is 4.5 litres. I then turned on tap on butt to run water through di with it running into another butt & within 3 hours had 210 litres of pure. Just an alternative to a submersible pump.