9.4.2 Physical parameters
Do you experience a taste while drinking potable water? Water in its natural state is tasteless, odourless and colourless. Although changes in these parameters may have no direct health effects, a slight change will result in consumer dissatisfaction. Important physical characteristics of drinking water quality are listed in Table 9.2.
| Parameter | Maximum permissible level | Adverse effect |
| Colour | 15 platinum-cobalt units (PCU)* | Unpleasing appearance |
| Odour | Not objectionable | Unappealing to drink |
| Taste | Not objectionable | Unappealing to drink |
| pH | 6.5–8.5 | High pH imparts taste and soapy feel, low pH causes corrosion. For effective disinfection pH is preferably |
| Turbidity | 5 nephelometric turbidity units (NTU)** | Visibly cloudy |
* In platinum-cobalt units the colour is measured by visual comparison of the sample with platinum-cobalt standards. One unit of colour is that produced by 1 mg of platinum per litre of solution (1 mg/l or 1 mg l–1), in the form of the chloroplatinate ion.
**The nephelometric turbidity unit is a measure of the turbidity of the water.
9.4.1 Microbial parameters