Working With Monopersulfate

Although monopersulfate is often used with mineral purification systems, it is gaining popularity among chlorine systems as well. That’s because monopersulfate requires only a short waiting period before swimmers can re-enter the water.

Here’s a look at the best ways to use this non-chlorine shock in conjunction with both chlorine and mineral systems, as well as how to test for it.

With chlorine

While monopersulfate cannot effectively sanitize pool or spa water, it is an effective shock treatment on chlorine pools. And it allows bathers to return to the water sooner — typically in less than 30 minutes.

That’s important, because though chlorine is far and away the most popular sanitizer used today and can quickly and effectively sanitize pathogenic bacteria and viruses, it requires occasional shocking treatments. Shocking the water gets rid of excessive chloramines — odorous byproducts of oxidation that can cause nasal and eye irritation — and requires raising the chlorine level to approximately 10 ppm.

But after superchlorinating the water this way, swimmers have to wait until the chlorine residual comes down to the acceptable range — between 1 and 3 ppm — before getting back in the water. This can take hours, depending on how high the chlorine level gets. This is where a non-chlorine shock becomes useful.

Monopersulfate can eliminate impurities through oxidation, and conserve the chlorine residual for killing bacteria. It doesn’t leave behind irritating or unpleasant byproducts or odors when it oxidizes wastes.

With mineral systems

Mineral purification systems and other alternate methods of sanitization have been growing in popularity of late. These systems use dissolved minerals like copper (to kill algae) and silver (to kill bacteria) and are ideal candidates for monopersulfate use.

While these minerals can keep your pool or spa safe from pathogenic organisms, minerals are incapable of oxidation. So, a monopersulfate residual is maintained in the mineral purification systems to oxidize wastes and debris. In such systems, where the level of chlorine or bromine is quite low or even non-existent, the monopersulfate residual level will stay in place much longer. The combination of minerals to sanitize and monopersulfate to oxidize provides protection similar to that of chlorine.

The test

Whether used in chlorine or mineral systems, monopersulfate should be measured after each use to ensure proper oxidation of wastes.

There are few kits available to test for monopersulfate. Almost all testing methods have chlorine interference, meaning that the chlorine level interferes with the monopersulfate test results. These tests actually depend on oxidation of an indicator by monopersulfate. But since chlorine is also a strong oxidizer, it usually causes false positive results in monopersulfate tests.

One company makes a subtractive testing method that gives an accurate monopersulfate value even in the presence of chlorine. First, it registers the total oxidizer value by a chemistry that detects both chlorine and monopersulfate. Second, the user completes a test that detects chlorine but not monopersulfate. The difference between the first value and the second value is the monopersulfate value.

Accurate measurement of monopersulfate in pools and spas that employ mineral purification systems is easier. Because chlorine is not present in significant concentrations in these systems, test strips or kits that allow chlorine interference give correct values despite the interference.

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