NC State Extension

Before Sampling

  1. Contact the selected laboratory (NC Labs for Generic E. coli Testing, NC Labs for E. coli and Coliform Testing with Prices) prior to collecting the sample (sample delivery (accept samples) times, collecting instructions, pricing per sample, testing method, etc.)
  2. Collect samples from cold water tap in sterile containers, usually provided by the testing laboratory.
  3. Do not open container until just before taking the water sample. Never set the cap down or leave it off longer than it takes to collect the sample. Hold the cap so that it is facing down to avoid having debris settle in it.
  4. Do not rinse sample bottles prior to taking samples. This may introduce residual chlorine into the bottle and kill bacteria (not for surface water).
  5. Use a new pair of rubber gloves for each sample.
  6. At no time should the sampler’s fingers come in contact with the inside of the sample container.
  7. Using a marker record the date, sample location, and sample time on an unopened container.
  8. It is undesirable to take samples too near to the bank or too far from the point of drain off, or at depth above or below the point of drain off.
  9. Take a sample at or near the pump connected to the surface water source by inserting a Tee in the line on the outlet side.
  10. If more than one sample is to be tested, all samples should be collected within 18 hours.
  11. The time between collection and start of analysis shall not exceed 24 hours.
  12. Always take extra bottles and sample request forms.
  13. Select your method for testing: the Colilert® method (24 + 2 hrs, Generic E. coli and coliforms) is recommended with quantitative results (not presence/absence).