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1. Sampling point Where possible, samples are to be taken 30 centimetres below the water's surface and in water that is at least one metre deep.

2. Sterilisation of sample bottles Sample bottles are:

— to undergo sterilisation in an autoclave for at least 15 minutes at 121 oC, or — to undergo dry sterilisation at between 160 oC and 170 oC for at least one hour, or — to be irradiated sample containers obtained directly from manufacturer.

3. Sampling The volume of the sampling bottle/container is to depend on the quantity of water needed for each parameter to be tested. The minimum content is generally 250 ml. Sample containers are to be of transparent and non-coloured material (glass, polyethene or polypropylene). In order to prevent accidental contamination of the sample, the sampler is to employ an aseptic technique to maintain the sterility of the sample bottles. There is no further need for sterile equipment (such as sterile surgical gloves or tongs or sample pole) if this is done properly. The sample is to be clearly identified in indelible ink on the sample and on the sampling form.

4. Storage and transport of samples before analysis Water samples are to be protected at all stages of transport from exposure to light, in particular direct sunlight. The sample is to be conserved at a temperature of around 4 oC, in a cool box or refrigerator (depending on climate) until arrival at the laboratory. If the transport to the laboratory is likely to take more than four hours, then transport in a refrigerator is required. The time between sampling and analysis is to be kept as short as possible. It is recommended that samples be analysed on the same working day. If this is not possible for practical reasons, then the samples shall be processed within no more than 24 hours. In the meantime, they shall be stored in the dark and at a temperature of 4 oC ± 3 oC.