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Bio-Lab presently distributes a liquid cyanuric acid (CYA) test reagent and a tablet form of CYA test reagent. These tests exhibit some different properties.

Liquid Type

Equal volumes of liquid CYA reagent and test water are mixed and added to a graduated column. CYA and liquid reagent form a cloudy mixture. When the cloudy test solution had been added to sufficient depth to hide a dot in the base of the receiving column, the liquid level is compared with numbers on the column's side.


Possible errors in this method are:

  • Interference by high chlorine levels will cause low results.
  • If the test mixture is over 23°C, a falsely low reading will result. The test reagent and/or water sample should be chilled to attain a temperature of less than 23°C.
  • Insufficient reaction time (less than two minutes), especially with low levels of CYA. If the reading is made too quickly, a falsely low reading will occur.
  • Crystallization of chilled liquid reagent. If crystals form in cold test reagent, the reagent should be warmed enough to redissolve all the crystals. Failure to do this will result in an erroneous CYA reading and may ruin the whole bottle of reagent.
  • Sedimentation or mouldy test reagent. Test reagent should be clear. Discard any questionable reagent.
  • Film or dirt over the target dot in the bottom of the test column will result in falsely high readings.
  • Already very turbid water samples will yield falsely high results.

Tablet Type

Test sample is added to upper line of larger test kit chamber. A CYA reagent tablet is then added and crushed with a dipstick. The resulting cloudy suspension is allowed to just hide a target dot on the foot of the dipstick by moving the dipstick to the appropriate level. The CYA concentration is read from the numbers on the dipstick at the upper fill line on the test kit chamber.


Possible errors in this method are:

  • Interference from high chlorine levels will yield low results. All chlorine should be neutralized before testing.
  • If the water is too warm, the test results will be falsely low. Water sample should not be warmer than 23°C.
  • Insufficient wait time, especially with low CYA levels. Low results will be obtained if the reading is taken in less than two minutes.
  • Film or dirt over target dot will give falsely high results.
  • A very turbid water sample will result in higher than correct readings.


The above information is supplied by Bio-Lab and represents its best interpretation of available technical information at the time of preparation. The sole purpose is to supply factual information to Bio-Lab customers. It is not to be taken out of context nor used as support for any other claim not made herein.