I've installed a 5 stage filter for the tap water, TDS has stayed the same as the tap water, about 350, TDS in most bottled water ranges from 90 to as low as 9, seemed strange the TDS didn't change with the filtered water, so tested for metals in both, Tap and filtered, none showed up in either, tested the PH in all, tap filtered and bottled. Tap and filtered both 7.5 all the rest slightly below, some as low as 5.5. Rechecked the filtered TDS result by putting in rusty nails overnight, yep TDS way high and showed up on metal test. Tests used were litmus strips for PH different ones for metals, chlorine, nitrates etc. So is there something that doesn't show on these tests to make the tap water undrinkable and why hasn't the filter changed the TDS? Am in Krabi town if this makes any relevance. Obviously I don't know enough about the science of water and would appreciate advice before I screw up my body totally!! Thanks.