Legionella testing of drinking water can be conducted by either a private service provider, including a private water treatment company or individual, or by the sole operator, as long as they are qualified and are properly monitored. The level of safety required is usually quite high, particularly where individuals will be taking medication in the home, such as for hypertension. This means that even though the risk of carrying legionella by-products through drinking water would be high, an organisation is permitted to carry out internal legionella testing more like the home-based legionella risk assessment as well.
This type of testing water sources can be undertaken by companies through accredited external sampling points. These sampling points are usually placed on premises where there is a known presence of legionella bacteria. They can also be situated close to known drinking water sources, although this is not necessarily necessary as the sampling point may simply be located near or on the water source itself. It is however necessary to keep the sampling point as clean as possible to ensure the best results from the sampling.
Sampling points may also be chosen randomly in an attempt to minimise the chances of false-positive results (illusation), which can often occur when using random sampling methods. The most efficient way to collect samples, whether from homes or from water sources, is via the use of special biodegradable sample collection containers. These sampling bottles are made from PVC and are therefore disposable, making them suitable to be used in a number of situations. The biodegradable containers have a specially designed cover that prevents the growth of bacteria, which means there is absolutely no risk of disease. Once the entire container has been emptied, it can be washed and reused.