Simon Posted June 6, 2011 Share Posted June 6, 2011 Two questions really:1) What is the Javel concentration to get a 650MVa reading on the Chlorine sensor I have (it's a Procopi but not sure if this is relevant). The reason is the doser is now acting very temperamentally and I need to be sure it's calibrated correctly). Also, as an aside, do the sensors need maintenance or replacement. Ours is currently 4 years old.2) Can CYA disappear/breakdown. Last year I had too high CYA, but this year there is no CYA measured on the Scuba+ tester. There has been rain etc and backwashing but not enough to replace all the pool water.Many thanks in advance.... Link to comment Share on other sites More sharing options...
Théière Posted June 6, 2011 Share Posted June 6, 2011 Concentration varies but the usual 1-1.5ppm should be enough. (lots of things throw the MVa out including CYA) Yes the probes usually need replacing, new probes usually come with a buffer (calibrating solution)It does seem that a bacteria can breakdown CYA, Chemgeek has done a fair bit of study on this but it does seem to happen on occasions. I am wondering if this is also causing your problems with the doser.Can you get a free/total chlorine reading with the scuba? Link to comment Share on other sites More sharing options...
Simon Posted June 7, 2011 Author Share Posted June 7, 2011 Many thanks Théière.I get a Total Chlorine reading on the Scuba+ (around 1.5ppm), and, if I add Chlorine (Javel directly) this will go up (eg I had 4ppm after adding Javel last week) but have not been able to get a Free Chlorine reading at all (it reads "Lo").You mention the probes need replacing - how often would I need to do this?Thanks Link to comment Share on other sites More sharing options...
Théière Posted June 7, 2011 Share Posted June 7, 2011 Hmm, sounds like the scuba+ may have developed a fault. Electrodes need replacing when they won't calibrate any more, they do require gentle cleaning from time to time, best to use the O/H tooth brush whilst they are out [6] Link to comment Share on other sites More sharing options...
chem geek Posted June 8, 2011 Share Posted June 8, 2011 If the FC is truly low and the TC higher, then that implies Combined Chlorine (CC) higher and could very well be bacterial conversion of CYA into ammonia. You can do a bucket test to see how much chlorine it will take before you get an FC reading. 1/4 teaspoon of 6% bleach in 2 gallons is 10 ppm FC. Or for 10% Javel this is 1 ml in 10 liters for 10 ppm FC. Link to comment Share on other sites More sharing options...
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