Quick Definition:

Potassium Peroxymonosulfate, more commonly called non-chlorine shock, is a substance that can rapidly oxidize swimming pool contaminates without the use of chlorine.

What is Potassium Peroxymonosulfate in swimming pools?

Potassium peroxymonosulfate is also called MPS, or Potassium Monopersulfate.  MPS does not contain chlorine, as it is a potassium salt of peroxymonosulfuric acid.

Potassium peroxymonosulfate is marketed as a popular non-chlorine based shock.  Its primary swimming pool use is to oxidize any contaminates in the water, leaving chlorine or bromine sanitizers already present in the water to focus on sanitizing the water.

There are several advantages of using potassium peroxymonosulfate in swimming pools:

  • Since there is no chlorine added, the swimming pool is available for swimming immediately after the shock has dissolved and time has been given for the oxidation process to complete.  Oxidation is usually complete in about one to two hours, versus eight or more hours for chlorine-based shock.
  • Chlorine use can decrease, as less chlorine is needed to oxidize organic and inorganic matter in the pool.

There are several disadvantage of using potassium peroxymonosulfate as a shock treatment in swimming pools

  • Chlorine tests can read incorrectly high in DPD or FAS-DPD tests, as the non-chlorine shock may show up as combined chlorine in these tests.
  • More expensive than chlorine-based shock products.
  • If adequate chlorine sanitizer levels are not maintained, then adding non-chlorine shock like MSP may increase the risk of algae growth due to possible nitrate creation from adding MPS.


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