(b) Place of collection. It has been suggested that the pool be sampled
at the shallow end to obtain water of the poorest quality in the pool. This is not
necessarily true. The sampling point should be varied, but preferably near groups of
swimmers. Do not have a swimmer collect a sample from the middle of the pool to
avoid collection of heavily chlorinated return water. Avoid this problem by collecting
samples at points between return water inlets.
Technique of sampling.
(a) First carefully remove the cap and stopper from the bottle. Be
careful not to touch the inner surfaces of the stopper.
(b) Hold the bottle near its base at a 45 angle.
(c) Fill the bottle in one slow sweep down and through the water. Be
sure the mouth of the bottle is always ahead of your hand, and take care to avoid
(d) Replace the stopper and the cap. Do not rinse the bottle in the pool
or the sodium thiosulfate will be removed.
(4) Disposition of samples. The samples should be refrigerated immediately
upon collection and held at less than 10C during transport to the laboratory. The
samples should be tested within 6 hours of collection. Pertinent data such as sampling
time, location of the sample, sampler's identification, and desired analysis should
accompany the sample.
b. Bacteriological Analysis of Pool Waters.
(1) Testing for coliform bacteria. The coliform organisms, most of which are
harmless, are present in large numbers in the intestinal tract of man and other warm-
blooded animals. The normal feces of man contain 100,000 to 1,000,000,000 coliform
organisms per gram. Coliform organisms are easily tested for, and the test is sensitive.
No appreciable quantity of fresh fecal material can be present in water and escape
detection when the coliform test is properly carried out.
(2) Interpreting test results. TB MED 575 states that when the membrane
filter procedure is used, not more than 15 percent of the samples may show more than
1.0 coliform organisms per 50 ml during any 30-day period.
(3) Example. A swimming pool has had 20 water samples taken for
bacteriological analysis during the last 30 days. Two of the samples had coliform
counts of 1.0 per 50 ml. Does this pool meet the standards for bacteria count?
(a) Answer: Yes.