pH value water quality

Another term to be considered is the pH value; this is not an impurity or constituent but merely a numerical value representing the potential hydrogen content of water - which is a measure of the acidic or alkaline nature of the water. Water, H₂O, has two types of ions - hydrogen ions (H⁺) and hydroxyl ions (OH^-).

If the hydrogen ions are predominant, the solution will be acidic with a pH value between 0 and 6. If the hydroxyl ions are predominant, the solution will be alkaline, with a pH value between 8 and 14. If there are an equal number of both hydroxyl and hydrogen ions, then the solution will be neutral, with a pH value of 7.


Acids and alkalis have the effect of increasing the conductivity of water above that of a neutral sample. For example, a sample of water with a pH value of 12 will have a higher conductivity than a sample that has a pH value of 7.

Table 3.9.3 shows the pH chart and Figure 3.9.7 illustrates the pH values already mentioned both numerically and in relation to everyday substances.

Table 3.9.3
The pH scale

Fig. 3.9.7
pH chart