Demo photo

 The following photo is of a R-Card of unknown origin. It is included for demonstration purposes only.

Each blue dot indicates the presence of E.coli in a 1 ml sample

    row 1 = 1

    row 2 = 12

    row 3 = 49

    row 4 = 43

    row 5 = 45

    row 6 = 13

total = 163

Because the accepted unit of measurement is colony forming units of E.coli per 100 ml sample, we multiply 163 x 100 giving 16300 cfu/100ml 

In practice we will be examining 3 cards for each test and recording the mean/average of the 3 cards.

Because 16300 is greater than 900 the Environment Agency would classify this sample as "poor", and advise against swimming. Me too ( I hope samples from the Thames are not a polluted as this ).