I've been using the Feedchlor and Dechlor products for several years now, and they usually work exactly as expected. I always buy a batch including one 10 kg drum of each product. But this year's batch (bought around March 2024) gave us some problems. The Feedchlor was OK - we achieved the expected chlorine concentration using the expected amount of Feedchlor. But we had to use much more Dechlor than expected to neutralise the chlorine. We had to use 2-3 times as much Dechlor as Feedchlor. We used all the testing techniques at our disposal to check our findings (Palintest "disc" comparator 0-50 mg/litre with chlorine HR and acidifying tablets, also the chlorine test strips, and finally DPD1 tablets to confirm removal of chlorine) so we're quite confident that our measurements were consistent. Fortunately, we discovered the problem while treating the smaller of our two tanks. We then realised that we would not have enough Dechlor if we completely filled our larger tank, so we took the precaution of only part-filling that larger tank before we added the Feedchlor, and that turned out to be a good move. At the end of our process, the Feedchlor drum is still about 80% full and the Dechlor drum is only about 30% full. Serial numbers from the drums: Feedchlor 2312012, Dechlor 2308033. I'd be grateful for any comments.