potassium peroxymonosulfate shows as CC

[ds18425]

I have a question about the non chlorine shock (potassium peroxymonosulfate).
How long does it give false CC readings? I cant shut down my pool for 1-3 days using the super-chlorination method (kids will kill me). Other than the expense is there any issues using the potassium peroxymonosulfate over super-chlorination?

 

[chem geek]

MPS shows as CC in a DPD chlorine test, but it shows up as FC in a FAS-DPD chlorine test. The reason is that it does not react with the dye itself, but does react with potassium iodide (the CC measuring reagent) in the DPD chlorine test and it reacts with the FAS-DPD titrating reagent during the FC part of that test. Taylor makes an interference remover, the Taylor K-2042 that will let you measure the chlorine vs. MPS readings separately.

As for how long it takes for the MPS levels to drop, that depends on how much there is to react in the pool. Usually it's a day or two. Note that some people still use their pools right after initial shocking, just when the chlorine levels start to drop from shock level. The active chlorine level is still a lower during shocking (around the equivalent of 0.6 ppm FC with no CYA) compared to most indoor commercial/public pools (around 1-2 ppm FC with no CYA).

Also note that when a pool is properly maintained, you don't need to shock it regularly.