WaterWorks™ EZ Coliform Cult

We have private spring. The water quality is analyzed once a year by a professional laboratory. This year we had coliforms and e.coli in our water. The professional analysis is expensive and so I tried to check it by myself with these tests. The plan was, to do another official test only after 3 negative tests of this water test. But this test is not so easy to use as I thought. The test must be incubated for 24 hours at 35°C or 48 hours at 25°C. The first test I tried at around 21°C in the living room, assuming, that I must wait around 60 hours in total. The test kept yellow. Another test where we put in our fingers (3 persons) was also yellow after 60 hours. A test of the same water without contaminated with our fingers and incubated at around 30°C was blue after 30 hours. Well, the test doesn't work below 25°C. A yellow test after 24hours at 35°C changes to blue after 48hours. Is it positive or negative? A test with an UV-LED creates fluorescence even in a fresh yellow bottle. I think the UV-test is only possible with a very specific light source, but not with an UV-LED. The test might be good if you use it in the right way. But the user manual is very short an because of that, many handling errors are possible.