A lot of nonsense - the rejection rate of the merlin is about 3:1, anyway, how much does 1000ltrs tap water cost you? Is it really a big concern, plus the RO-man units are so slow, very good but slow (i've had 2 so I know what I'm saying here plus an AquaFX ro), you can reduce the rejection rate of the merlin if you are so worried about spending an extra £1 a week on water. Tap TDS 350, out of merlin at 3/4, 1.2ltrs/min @45psi