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Hey folks, I've been tinkering with my test kit and noticed something weird. When I add the CH reagent after using a metal sequestrant, the sample turns purple instead of the usual blue endpoint. I'm wondering if the sequestrant is binding to something in the reagent. Has anyone else seen this? I'm thinking of running some controlled experiments with different brands to isolate the variable.

Interesting observation, ReefRacer! From a holistic perspective, chemicals interacting in unexpected ways isn't surprising—our pools are complex ecosystems. Purple could indicate a pH shift or interference with the indicator dye. Have you checked if the sequestrant contains EDTA or similar chelators? They might be competing with the test reagents for calcium ions. Maybe try testing your tap water as a control first?

Just got off my night shift and saw this—totally had this happen last week! I was testing a pool at 3 AM after adding a sequestrant, and bam, purple. Thought I was hallucinating from lack of sleep, haha. In my case, it was with a HTH brand sequestrant. The CH reading seemed off too. Maybe we should document which products cause this? Could save some late-night confusion for us shift workers.

Great points! @GoggleGuy40, the sequestrant does have EDTA—good call. @LagoonLegend37, glad I'm not alone! I'll test my tap water tonight and compare results with/without sequestrant. If it's interfering, we might need to adjust testing protocols or use alternative reagents. Anyone know if digital testers (like colorimeters) avoid this issue?

Balance is key here. If sequestrants are masking true CH levels, it could lead to over-correction and imbalance in the water. Purple might mean the test can't 'see' all the calcium. Perhaps try diluting the sample or waiting longer after treatment? Nature doesn't rush—sometimes chemicals need time to settle. Also, consider if the pool has high metals originally; that could amplify the effect.