Something fishy: an operator can't figure out why his chlorine tests keep showing up negative--until a major fish kill reveals the problem.(lessons learned)

John was the operator of a rather antiquated 120,000-gallon steel pool at Penn State University that had recently had its pumps and filters replaced. Naturally, when the work was finally completed, John, a veteran operator, was excited to see how this modern equipment would cut down on his workload.

Unfortunately for him, and a whole lot of fish, he forgot that even the nicest equipment is only as good as the person running it.

At first, everything was going great--the pool looked and smelled cleaner than ever. So imagine John's surprise the next morning when he arrived and did his first chlorine check. After putting the drops of DPD No. 1 and No. 2 into the test vial, he found the sample water to be perfectly ... clear.

Immediately, he checked the 150-pound chlorine gas cylinders and found what he thought was the reason: both cylinders were empty. Without thinking twice, John simply replaced them. Before leaving for the day, he did his last chlorine test. Again, he was surprised to find the test vial clear and the gas cylinders empty. Maybe it was just the new water and pump system, he thought, and put two more cylinders in place before leaving for the day.

But the next morning the same thing happened. At this point it might have become clear to anyone who's gone through operator certification training what was going on.

But John had none of that training. He did, however, have lots of chlorine. So each time the test vial showed clear, he just kept adding it.

After three days of this fiasco, John decided the easiest way to resolve the problem was to dump the entire pool and start from square one (sodium thiosulfate--what's that?).