What impacts water quality
The way we treat water depends on the source, so any particular water supply works may use one (or more) of the processes below.
Water from springs and boreholes is generally higher quality and may only need basic treatment followed by disinfection. Water from sources such as rivers, lakes and reservoirs normally requires more complex treatment as it may contain more impurities (for example, pesticides) that need to be removed.
If water seeps through the ground until it reaches rock that it can’t penetrate, it forms underground aquifers. The water in these aquifers is called ‘groundwater’ and is often very high quality because as it seeps through the ground, many contaminants are naturally filtered out. It also tends to be hard water.
We monitor the quality of our raw water sources to make sure they haven’t become contaminated – and also to decide which type of treatment to use for a particular source of raw water.
Why we test water quality
It's our duty to ensure a wholesome supply of drinking water for our customers.
The Water Supply (Water Quality) Regulations set the standards required for this. They explain, in detail, the levels of certain characteristics, elements and substances that are allowed in drinking water to protect public health, and how much of each substance should be in the water supply.
Usually, the limit is a maximum level but occasionally a minimum value is also set (for example, the pH, or acidity levels). This level is known as the Prescribed Concentration or Value (PCV).