Can water filter affecting PH level?

[GettingFiesty]

How would (or can) a water filter change the PH level? In one of the other forums somebody is saying that their RO/DI unit is changing their PH. I thought they just pulled out impurities. Is this possible?

Thanks.

[Randy Holmes-Farley]

Yes, an RO/DI can change pH a lot. It theoretically pulls out everything that impacts and controls pH, so the pH can change a lot.

Do not, however, worry about the pH that you might measure with a meter or a kit. Neither can accurately read pH in pure water, and a low real or apparent pH in such water is not the cause of or a significant contributor to low pH in reef aquaria.

FWIW, pure water in contact with air has a pH well below 7 due to dissolving CO2 from the air. It forms carbonic acid when in contact with water.

[GettingFiesty]

Wow. Thanks. Learn something new here on RC everytime I turn around.

Thanks Randy and Happy New Year!

[Randy Holmes-Farley]

You're welcome and Happy New Year to you too. :)