5 Monivong Boulevard, P.O Box. 983, Phnom Penh, Cambodia accueil@pasteur-kh.org

Standard Operating Procedures for Sampling

Well Water​​ for Physico-chemical Analysis


I. Guidelines for different sampling material

1.​​ For material

  • Pens/wax crayons

-  ​​ ​​​​ Sample bottles, labels and marker pens

-  ​​ ​​​​ Sample storage/transit containers and ice packs

-  ​​ ​​​​ Filtering apparatus (if required)

-  ​​ ​​​​ Samplers/sampling equipment

-  ​​ ​​​​ Rubber boots, waders, etc.

-  ​​ ​​​​ Standard operating procedures for sampling

-  ​​ ​​​​ Spares of all above items if possible and when appropriate

2.​​ For documentation

  • Pens/wax crayons

  • Sample labels

  • Field notebook

  • Report forms

3.​​ Safety

  • First-aid kit

  • Waders, gloves, etc.

  • Fire extinguisher (if appropriate)

4.​​ Transport

  • Does assigned vehicle have sufficient capacity for personnel, supplies and equipment?

  • Is vehicle road-worthy? Check battery, lubrication, coolant, windshield washer

  • Is there sufficient fuel for the trip, either in the tank, in fuel cans, or available en route?

  • Is the spare tire inflated, is there a jack, wheel wrench and tool kit?

5.​​ Double-check

  • Itinerary

II. Sample containers

  • Containers for the transportation of samples are best provided by the laboratory. This ensures that large enough samples are obtained for the planned analyses and​​ that sample bottles have been properly prepared, including the addition of stabilizing preservatives when necessary.​​ 

  • It is essential to have enough containers to hold the samples collected during a sampling expedition.

  • Sample containers should be used only for water samples and never for the storage of chemicals or other liquids. Glass containers are commonly used and are appropriate for samples for many analyses, but plastic containers are preferred for samples intended for certain chemical analyses or for biota or sediments. Plastic has the obvious advantage that it is less likely to break than glass.

  • Sample containers must be scrupulously clean so that they do not contaminate the samples placed in them. Some technicians fasten a Kraft paper cover over the bottle caps before autoclaving to protect them from contamination during handling. The neck of the bottle should not be plugged with cotton wool.

  • To prepare sample bottles, they should be washed with a non-ionic detergent and rinse at least three times​​ (five is better) with distilled or de ionized water before autoclaving. New bottles require the same preparation. If distilled or de ionized water is not available, clean chlorine-free water may be used.

III. General guidelines for sampling ground well water and other sources

The following general guidelines can be applied to the collection of water samples (to be analyzed for physical​​ or chemical variables) from rivers and streams, lakes or reservoirs and groundwater.

1.​​ Samples for physical and chemical analyses.​​ The minimum sample size varies widely depending on the range of variables to be considered and the analytical methods to be employed, but it is commonly between 1 and 5 liters.

2.​​ Groundwater samples are normally obtained from existing drilled wells, dug​​ (shallow) wells or springs. Occasionally, during the course of a hydro-geological survey, test wells may be drilled and these can​​ be used for monitoring purposes.

3.​​ If the groundwater source is a flowing spring or a well equipped with a​​ pump, the sample can be obtained at the point of discharge. The water should flow for several minutes before sampling until it has reached constant conductivity or temperature in order to avoid any water resident in the system’s piping being taken as a sample (the piping material may have contaminated the water). Care should be taken to ensure that no air bubbles are introduced to the sample while the bottle is being filled, since this could alter the dissolved oxygen concentration.

4.​​ The sampling container must not be allowed to touch the bottom of the well or spring catchment since this would cause settled particles to become resuspended and to contaminate the sample.

5.​​ Before collecting any sample, make sure that you are at the right place. This can be determined by the description of the station, from the position of landmarks and, in lakes, by checking the depth. If samples must be taken from a boat, a sampling station may be marked by placing a buoy at the desired location; otherwise it is necessary to identify the sampling station by the intersection of lines between landmarks on the shore.

IV. Sampling from dug wells and similar sources

1. Prepare the bottle. With a length of string, attach a weight to the sterilized sample bottle (see Figure). Open the sterilized bottle​​ as described in step 5 above.

2. Fill the bottle (see Figure). Hold the bottle near its bottom and submerge it to a depth of about 20 cm, with the mouth facing slightly downwards. If there is a current, the bottle mouth should face towards the current. Turn the bottle upright to fill it. Replace the bottle cap.

3. Attach the bottle to the string. Take a 20 m length of string, rolled around a stick, and tie it to the bottle string. Open the bottle as described above.

4. Lower the bottle. Lower the weighted​​ bottle into the well, unwinding the string slowly. Do not allow the bottle to touch the sides of the well (see Figure).

5. Fill the bottle. Immerse the bottle completely in the water and continue to lower it to some distance below the surface (see Figure).​​ Do not allow the bottle to touch the bottom of the well or disturb any sediment or take the water at a depth of 30 cm below the surface.

6.​​ Raise the bottle. Once the bottle is judged to be full, bring it up by rewinding the string around the stick. If the bottle is completely full, discard a little water to provide an air space. Cap the bottle as described previously.

7.​​ Wipe vials, labeled and placed in the refrigerated container.

8.​​ Complete sampling sheet.

photo well sampling

Lowering a weighted bottle into a well

Table: Example page from a field notebook



Site​​  ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ N°/code  ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ Description


Station ​​  ​​ ​​ ​​​​ N°/code  ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​ ​​​​ Description


Date ​​​​ /____/____/____/  ​​ ​​ ​​ ​​ ​​​​ Time​​ /____/_____/


Weather conditions:



Sample collected​​  ​​​​ Standard chemistry​​ ​​ Yes/__/No/__/ ​​​​ ​​ Sample N°


Sampling depth:


Problems encountered/adaptations made during sampling:


Sample preservation and storage:


Sample transport:


General remarks:





Samples received by:



Data receiver by: