Just to add you can not measure the pH of RO or RO/DI water. These are usually false pH
readings. pH readings need ions in the water to give a accurate reading, especially RO/DI.
If it is just RO and you have a high tap water TDS then yes, often you can. Once the water
is exposed to ambient air it will pick-up CO2 and yield a pH usually lower than 7 often
around the 6 areas

--
Boomer

If You See Me Running You Better Catch-Up

Former US Army Bomb Technician (EOD)
Member; IABTI, NATEODA, WEODF, ISEE & IPS

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"Cindy" wrote in message
.com...
: My tapwater pH is 7.6.
: The water that comes out of the RO filter is 6!
: No wonder I can't keep my pH up. Do RO filters normally make the pH that
: much lower?
:
: Cindy