All available sources recommend using distilled water for performing a soil pH test.

However, distilled water by itself is anywhere between pH 5.5 and 6.5 due to dissolved CO2 (HCO3- ions).

In my case, the distilled water is pH 5.5 according to my test strips. When reading the actual soil pH is it necessary to reduce the reading by 1.5, or will I get a true reading without adjusting?

  • I'm going to suppose your test strips are not accurate enough to discern the difference due to ordinary room air levels of CO2.
    – Boba Fit
    Commented May 8, 2023 at 13:27

1 Answer 1


The pH of distilled water makes no difference when being used to make a solution with ionizing materials. The quantity of ionic material in the distilled water is negligible relative to the total.

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