Two tests are best suited for monitoring drinking water quality. The Presence/Absence (P/A) test mixes the water sample with a special broth medium, incubates the mixture overnight at ambient temperatures (between 20 C and 30 C), and depends upon a colour change to indicate the presence of contamination.

The hydrogen sulphide (H2S) test uses a treated paper strip that is incubated with the water sample. If bacteria are present in the sample, they produce hydrogen sulphide, which turns the paper black. The test can also indicate the severity of water contamination.

Two other tests are intended for monitoring water sources and recreational waters. The coliphage detection test indicates the presence of "coliphages," viruses that accompany fecal coliforms like Escherichia coli and prey on them. Fecal coliforms in water are a sign that other dangerous bacteria, viruses or parasites transmitted by people may be present. The water samples incubate overnight between 27 C and 31 C in petri dishes containing small disks of filter paper that hold the dried E. coli host bacteria. Clear spots in the dishes mean the bacteria have been prevented from growing because of coliphages, thus indicating contamination of the water with fecal coliforms.

The A-1 Broth test requires water samples to be incubated in a tube of culture medium at 44.5 C for 24 hours. If there are any fecal coliforms in the sample they will survive this heat and produce gas that will be visible in a second tube inverted inside the first tube.