(h) Set the incubator at 35-37C and place the reaction vessel inside of
it. Incubate for 24-28 hours (28 hours is the maximum time limit).
Incubate within 30 minutes of combining the water sample with the reagent
and mixing the solution.
Follow the operating instructions when setting up and calibrating the
(a) Read the sample vessels after 24 hours (up to 28 hours, if needed,
while incubation is at 35-37oC). The sample vessels will show one of two colors:
1 No color. This means that coliform and E. coli are absent,
making the water potable or safe to drink.
2 Yellow color. This means that coliforms are present and the
color will increase. Additional procedures should be performed.
(b) Place the carrier two inches from the ultra violet light in a dark area
if the color of the sample is yellow. Depending on the yellow color, one of the following
should be accomplished:
1 For a faint yellow or fluorescent coIor that you are unsure of,
compare it to the comparator (W103).
2 For a yellow color equal to or greater that the comparator,
interpret the sample to be positive.
3 For a yellow color that is slightly less than the comparator,
incubate the sample up to an additional 4 hours. The yellow color will increase if
coIiforms are present.
4 Confirm and record the coliform results.
The comparator should be dispensed into a vessel identical to the ones used
in the presence--absence coliform test, before comparing it to the reacted test
(a) Open each vessel and disinfect the vessel and contents. Add a
household bleach to the top of each vessel.
(b) Cap each vessel tightly and shake or mix.