On the testing end, we continued troubleshooting the non-return valve. So far, all the designs we’ve tested have been leaky! Also, we’ve been measuring unusually low concentrations of chlorine with our set-up, despite our highest-ever chlorine stock concentration (0.66%). The main goals right now are (1) obtain a sealing non-return valve to prevent back-flow of chlorinated water into our holding tank and more importantly, (2) move towards our goal of dosing 1 ppm consistently.
One other observation to take note of: our method for measuring the chlorine dose in our water samples involves the use of a reagent that turns pink in the presence of free chlorine. However, at too-high doses, the chlorine (bleach) completely oxidizes all of the reagent, leaving clear solutions that seem to be chlorine-free! Perhaps the reason we were observing seemingly low chlorine concentrations in our latest round of tests was that we were actually overdosing our water. This is one limitation to our testing methods to keep in mind in upcoming runs as we tinker with higher and higher concentrations of our stock chlorine.