What is a hot tub shock & why do I need it?

Why is a shock needed?

During hot tub use organic pollutants from bathers and their costumes unavoidably become dissolved in the water. These contaminants can include perspiration, body lotions, make-up, urine, soap and fabric conditiioner from costumes. Because these contaminants dissolve in the water they cannot be removed by the filter and so they continually accumulate until they eventually make the water dull, cloudy or foamy.

What does a hot tub shock do?

A hot tub shock is a chemical that you can add to the water to remove these pollutants by oxidising them.  In scientific terms, this means that the shock takes electrons from the pollutants and this process will breaks down the chemical bonds in the polluting substances allowing them to precipitate out of solution more readily.

A shock will also reactivate chlorine or bromine sanitiser by breaking apart the the bi-products of the sanitation process, the smelly chloramines or bromamines, and so producing more 'free' sanitiser.

There are three common types of hot-tub shock ...

1. Non-chlorine shock, such as Surespa Non-Chlorine Shock.  This is a straight-forward Potassium Peroxomonsulphate oxidiser which can be used regularly to break down pollutants.  It also breaks down chloramines or bromamines to generate more free sanitiser. It is mild, non-toxic and much the preferred means of shocking hot tub water.  The hot tub can be used 5 - 10 minutes after application. Non-chlorine shock can be used with any sanitiser.
2. Chlorine-based shock, such as Surespa Spa Shock Express.  This product contains Triclosene Sodium which, when dissolved in water, gradually releases hypochlorous acid, a potent form of active chlorine that acts as both a disinfection boost and an oxidiser to break down pollutants.  Toxic fumes can be released when this product is used and the tub should not be used for at least an hour after use.  The benefit of Spa Shock Express over Non-Chlorine Shock is that it can be more effective in treating heavy contamination. Spa Shock Express can be used with any Hot Tub Sanitiser.
3. Calcium Hypochlorite.  This is a non-stabilised chlorine that is added to the water to raise the chlorine level, or super-chlorinate, the water.  This approach can only be used if you are using chlorine as your every-day sanitiser and you will have to wait until the chlorine level has returned to a safe 1-3ppm before you enter the water again.  There are many reasons why it's not a good idea to super-chlorinate a hot tub, including skin irritation, eye discomfort, and breathing issues, as well as damage to the tub itself by corroding metal components, damaging pillows and bleaching surfaces

How often should I shock my Hot Tub Water?

The answer to this is: as often as needed.  There is nothing wrong with having a regular weekly or fortnightly shocking regime, but it probably isn't strictly necessary, and if you find that it is you should really be asking yourself where the pollutants are coming from and how can you minimise them.

In the interest of minimising chemical use the recommendation is to just use a shock as required when your water starts to look dull or get a bit foamy.

Always try a shock product first if the water starts to foam and only use an anti-foam as a last resort.