Getting reliable results from your testing kit is easier than you might think.
Some of it is just good housekeeping—you need to keep your testing equipment clean. Some is common sense—you need to be careful to not contaminate your water sample, reagent, distilled water or the instruments you will be using.
And then there is attitude. Can you be really scrupulous about measuring, cleaning and equipment maintenance? If yes, you are half way to a good result. For the other half, just follow these simple instructions of a consistently reliable tester:
Collect a representative sample
Make sure you do not collect your water sample at places where there may be a concentration or dilution. So avoid collecting a sample from near effluent/ clean water outlets. Avoid aeration areas and heat sources. Do not just skim the surface of the water. Dip the jar under the surface of the water.
Do not contaminate the sample
Contamination can occur if instruments are not cleaned properly, or are rinsed with a different sample, or gather impurities from a resting surface. Make sure field test equipment, especially, pipettes and droppers placed on the ground do not pick up dirt. Do not dip unrinsed dropper or pipette into a reagent or distilled water or water sample.
There is no shortcut to measuring carefully. Be OCD about measuring. If using a pipette, make sure to squeeze the bulb before you dip the pipette in the sample. This will help avoid air bubbles in the stem.
Calibrate. Calibrate. Calibrate.
Keeping a measuring tool calibrated is one of the most important maintenance disciplines you can establish for your testing kit. Most testing equipment manufacturers ship standards for re-calibrating equipment. Ask your testing equipment manufacturer how often the testing instruments should be calibrated. (ProWater kits, for example, need to be re-calibrated with every new top up batch of reagents)
Check test kit range
Kits are devised to test for a range. If you have a highly concentrated parameter, it might exceed this range. Then, you will need your testing kit to flag this, and not just indicate the highest possible concentration it can read. Look for testing equipment that alert for out-of-range readings. Once you know that you have a high concentration sample, you can dilute the sample and test.
Check the testing equipment manufacturer’s product data sheet to understand how temperature, storage, pH etc. might affect test results.
Store as per instructions
Away from direct light, or heat, ventilated. These instructions will be shared with you in the data sheet or instruction manual accompanying your kit.
Do not use chemicals past their shelf life.
Even for similar tests, quantities of reagent, or time taken to do the test might be different.
Observe as you test
Last but not the least. If observations vary from what you expect to see as per your instruction manual, call up the supplier of your testing kit. You might be looking at interference from other chemicals in your water sample.
That’s it folks. Happy testing!