SAMPLING PROCEDURES
To enable mixing of the sample in the laboratory before processing, leave ample air space (at least 2.5cm) above liquid level. Collect samples that are representative of the water being tested. Keep container closed until ready to sample. Do not contaminate inner surface of lid. Flush sample ports. Then fill container without rinsing using aseptic technique to avoid sample contamination. Close container immediately.

Potable waters
It is important to ascertain from the client what they require to be tested. For example, analysis of a drinking water sample from a residence utilizing a rain water tank, or storage tank from a bore, would require the sample to be collected from the tap used for obtaining the water directly for use. This sample will then test the whole system, direct water supply, pipe work, collection system and storage tank. If a mains water sample was required, it must be ensured that the tap utilised is connected directly to the mains supply and does not connect to a cistern or storage tank.

Open tap fully and let water run to waste for 2 to 3 minutes or sufficient time to allow clearing of the service line. Leave tap running, reduce water flow rate if necessary to avoid splashing or loss of additives and fill container.

If well water is to be collected and a hand pump is fitted, pump water to waste for 5 minutes before collecting sample. If a mechanical pump is fitted collect sample from a tap on the discharge, run tap to waste for 2 to 3 minutes before collecting sample. If a pump is not fitted collect sample directly from well by lowering a sterile container with a weight attached to the base.

Raw Potable or Raw Non-Recreational Waters
When collecting samples directly from a river, stream, lake, reservoir, spring or shallow well collect a sample which is representative of the source of supply. It is preferable to collect samples from such a position that equates to the draw off point. Take samples by holding bottle by its base and plunging it below the surface. Then turn the bottle slowly upward and the mouth is directed towards the current (if no current, move slowly away from hand). Where samples are collected from a boat, sample from the upstream side of vessel. If it is not possible to collect samples in this manner, attach a weight to the container and lower it into water. In any case avoid contact with the bank or stream bed.

Surface Waters
Stream waters sampling locations will be decided upon based on the purpose of the study. It is preferable to collect a baseline sample, upstream from the study area. Where investigation of the dispersion of waste waters is to be analysed, preliminary cross section studies may be necessary to determine completeness of mixing. Where a tributary stream is involved, select a sampling point near the confluence with the main stream. Samples may be collected from a boat or from bridges near critical study points. Sample collection is as described in Section 2, above. Choose a sampling frequency which is reflective of the stream conditions. For example, to evaluate waste discharges, sample every 4 to six hours and advance the time over a 7 to 10 day period.

Recreational Water - Not Swimming Pools
Sample locations should be selected based on the reason for analysis. Where discharge water contamination is suspected, samples should be collected adjacent to drains or natural contours that would discharge storm water or septic waste. Collect samples in a swimming area at a uniform depth of 1 meter. Sampling of the shallow water may also be required because of the exposure of young children at the water’s edge. Samples should be collected at the peak bathing time, usually on weekends. Sample collection is as described in Section 2, above.

Swimming and Spa Pools
When using the sampling cocks in the filter return or discharge lines, run to waste for 3 to 5 minutes before collecting sample. Where samples are to be collected directly from pool or spas sample where water depth is approximately 1 meter. Use a second sterile container to collect sample. To collect sample hold the second container (with lid off) upside down and plunge into water to a depth of approximately 20cm. Then invert container to fill and remove. Decant the sample into the container with Na₂S₂O₃.

Sediments and Sludges
Collect sample by aseptically scraping sediment into sterile container. Sampling frequency for reservoirs and lakes may be related to seasonal changes in water temperature. Sludges from water and waste water treatment purposes should be collected as directed by the client.

Cooling Towers
Fill container directly from free flowing water in tower basin by holding open container at approximately 45 degrees and immerse in water. Filling slowly to ensure there is no loss of Na₂S₂O₃, if present. When collecting from a sampling cock or discharge pipe, run to waste for sufficient time to allow removal of "dead" water from tubing. Minimal volume is 10mL. A preferred sample volume is 70mL.

Sample Size
The following table gives the sample size required for different analyses and water types. Primary recreational water is described as water used for bathing where immersion of body occurs. Secondary recreational water is described as water used for wading only.

Minimum sample volume required for analysis