This paper presents a practical guide to obtaining a representative sample of filter media at the point of manufacture and on the job site as well as providing insight into selecting a media testing laboratory and the pitfalls of the various tests performed on those samples. The AWWA B100 Standard for Filtering Material provides a quantitative basis for sampling but currently does not give procedural methods for obtaining representative samples. The B100 Standard Committee is drafting methods for the next revision. Until then, this paper provides several methods for obtaining representative samples and details the practices used to protect and identify them. The methods detailed are for sampling at the place of manufacture or at the project site. Sampling at the place of manufacture is recommended.

Once the samples have been obtained, they must be properly tested. Not all geologic testing laboratories are familiar with AWWA B100 media testing methods. This paper provides insight into selecting a testing facility that has the capability to test the samples in accordance with the AWWA B100 testing methods that are sometimes nonstandard. Because some of the testing methods are nonstandard, the paper identifies those AWWA mandated procedures that must be followed in order for the testing to conform to the AWWA B100 Standard. Some of these procedures can be identified in the test report as a quick check to ensure that the results are compliant.

The paper stresses the concept that a non-representative sample can provide erroneous test results no matter how well the laboratory testing. Likewise, improper laboratory testing technique can provide erroneous test results even with a good representative sample. To ensure accurate results, proper sampling and testing techniques must be followed meticulously.

Reprinted with permission from F. B. Leopold Company, Inc