Louisiana Department of Health & Hospitals | Kathy Kliebert, Secretary

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Heterotrophic Plate Count of Water

PHL Location

Central Laboratory, Amite Laboratory, Lake Charles Laboratory, Shreveport Laboratory

CPT Code



HPC, Standard Plate Count, SPC

Brief Description of Test

Heterotrophic Plate Count, also known as “standard plate count”, is a technique used for estimating the viable bacteria population in a water sample for aerobic and facultatively anaerobic bacteria .

Possible Results

colony count/ ml

Reference Range

30-300 colonies

Specimen Type

Drinking water, vending water, bottled water, dairy waters of all types, including recirculating cooling water and dairy water with glycol.

Specimen Container(s):

Drinking water and dairy water samples are collected in sterile, disposable, 100ml Nasco Whirl-Pak bags, each containing a 10 mg sodium thiosulfate tablet. Bottled waters are submitted in the containers in which they are sold.

Minimum volume accepted:

100 ml

Collection Instructions


Storage and Transport Instructions

Store and transport sample(s) in clean ice cooler. Dairy water samples must be at 0.0-4.4ºC upon receipt into the laboratory. Maximum time from collection until analysis is 8 hours.

Causes for Rejection

  • Sample > 8 hours old
  • Sample frozen
  • No sample ID
  • Unacceptable collection container
  • Insufficient sample
  • Sample leakage
  • Incomplete sample form

Limitations of the Procedure

Difficult to enumerate when bacterial population of sample is extreme.

Interfering Substances

Excessive chlorine, fungal growth.


DOLSOPDWM-02 Hetertophic Plate Count Method for the Enumberation of Heterotrophs in Drinking Water Pour Plate Method SOP of the LA DHH-OPH Laboratory.

Additional Information

Complete a Lab 8 Laboratory Request and Report Form. The following is required Lab 8 information: Sample sequence #’s and project code, name of supply, collected by (name or initials), PWS ID (if applicable), date and time of collection, type of sample and disinfectant residual (if applicable).