I have been asked many times why it is recommended to do heat tests when testing for po4.
Well first here is how it is done
take a sample of water to be tested and then heat to 80 degrees C now do your PO4 test and take the reading. Then allow a fresh un tested sample of the heated water to cool and test again, take reading.
Why do this.
When you heat the water the binding of PO4 from the water is removed and can be tested far more accurately, when normal tests are done, much of the PO4 (up to 3-4 times the amount) remains untested.
Try it and see
