All sites at times may have potential issues with their water either in storage or in line, regardless of being on a bore hole or mains supply.
It is very easy to contaminate a water sample whilst taking it, so the correct technique of collection is very important to avoid inaccurate results. Often a client may take a sample and when this occurs it is impossible to know how well the sample was taken.
Blow torches used to sterilize the water vessel outlet before a sample was collected. Most fittings are now plastic so this is not practical. Using an alcohol wipe first to clear any dirt from the tap/outlet pipe is very effective. Another method is to use methylated spirit on a swab attached to a piece of wire – set light to it and hold to the tap.
Water specimens for analysis and bacteriological examination need to be representative of the quality of the water supplied under normal conditions of use, otherwise the results will be misleading.
- Wear disposable gloves.
- Label the plastic sample pot before taking the sample (you can’t write on a wet pot).
- Clean the tap/pipe/outlet with an alcohol wipe or wipes thoroughly. This can be achieved by pushing the wipe up into the tap aperture and twisting it around. Also clean the outside of the tap to clear away any dust which could potentially drop into the sample.
- Turn on the tap and let the water run into a white bucket for 2 minutes. This will remove any stagnant water, especially if taking the sample from the end of a nipple line. It will also push out any debris stuck in the tap/outlet which may contaminate the sample unnecessarily.
- Wearing disposable gloves take the top off the pot and let the stream of water run into the pot and completely fill it. Do not touch the inside of the lid, put the lid down or touch the open top of the pot with the tap/outlet pipe– if you do discard and take another sample.
- Seal and send off for testing asap. The most accurate results are obtained within 6 hours of sampling. Refrigerate overnight if necessary.