Hi,ive a new set up with pure freedom 300GPD system,includes 10"DI vessel, only refilled water tank approx 10 times prob 2000-3000 litres,TDS meter initally read 000, now reading 004.Is this normal after just a couple of weeks use?what is the max reading i should use the water at?ive been told up to approx 8-10 is this correct. cheers dave