Spa Shock Guide
If the water in your spa or hot tub is cloudy and odorous, or has algae and other biofilm, it is typically easy to fix by adding a spa shock treatment. Shocking a spa involves adding a super-dose of chlorine or non chlorine (potassium monopersulfate or MPS for short) to the water. This breaks down the organic waste contaminants and any chloramines (combined chlorine) that are present allowing your sanitizer to perform at peak efficiency. Spa shock also works with ozone and bromine spas. For bromine spas the treatment converts bromine ions to hypobromous acid, a highly effective sanitizer.
While more expensive than chlorine shock treatments, most spa experts recommend the use of a non-chlorine shock containing MPS. This type of shock treatment is oxygen based and is often referred to as OXY shock. It works for pools as well as spas with the advantage that there is less downtime. Swimmers and spa users can usually enter the water soon after applications. (Note: always follow product instructions carefully as some may require a longer wait period.) A second advantage of using non chlorine products for both spa shock and pool shock treatments is that they won’t bleach of harm vinyl liners or surfaces.
Non chlorine spa shock is not strictly speaking a sanitizer so needs to be used with a sanitizer system (chlorine, bromine, ozone etc). For fresh water fills a spa chlorine shock is normally recommended. This can be followed by regular non-chlorine shock treatments after a residual chlorine or bromine level has been established in the spa.
Some non chlorine shock treatments are a blend oxidizer and flocculant combination (sometimes referred to as oxidizing flocculant) with some spa and pool users reporting excellent performance. Chlorine free spa shock is fastier dissolving than chlorine shock and owners do not run the risk of raising water calcium levels. The amount of spa shock treatment to use will depend on the bather load and type of sanitation system being used.
Note: Spa shock will destroy biguanide polymers and as such is not compatible with biguanide pool and spa systems.