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Okay, you are doing great.  Your water was correctly balanced, and now you have something in there to stop things from growing.  But you are not done yet.  One last thing to do - but it is really easy.





Once you've killed the bad stuff in your "step two", you need to remove the contaminants from your spa.  If you neglect this step, you spa can be technically "sanitary" - but the water will still be cloudy, with perhaps a musty odor, and generally not very pleasant.  "Oxidizing" the contaminants removes them from the water, leaving it looking and smelling as sparkling and fresh as when the hot tub was first filled.

The method of ozidizing (also called "shocking") you will utilize is directly related to which method of sanitizing you choose for your spa.  One type is made for one system, and another for a second.  Here is what you would have to do:


This is where the high-performance salt water systems shine.  Since the system generates its own ozone and MPS (two oxidizers) you don't need to add any yourself. The spa is continually oxidizing the impurities on its own.  So you don't have anything to do!  The spa is doing this step for you as well.

If you don't have a high-performance design (one that only generates chlorine) you will still need to add some shock.  The simplest option is a chlorine-based version, with a small amount typically added one time per week.

Pros:   High-performance systems are easier than any other method - nothing to do. Spa automatically oxidizes.  

Cons:  Basic after-market systems still require a minimum of once-a-week maintenance.


Ozone (o3) is a very effective oxidizer.  In fact, ozone is regularly used in commercial buildings to sanitize the air ciruclating systems.  Spas have ozone generators that inject the ozone into the spa water.  When used with spas, the ozone has a very short life - the "bubbles" you see at the output are actually are in breathable (o2) form.  The actual ozone has already done its job deep within the spa.

However, if any water doesn't make it past the ozone injector, it's impurities will not be oxidized.  Meaning, the water behind the jets, on the uper parts of the spa shell, on the bottom of the spa cover, etc. are not being treated by the ozone.  Another oxidizer needs to be used to offer complete oxidation.  "MPS" - a powdered, non-chlorine oxidizer - is the most commonly used shock for ozone systems.  A small amount is added each time the spa is used.

Pros:   No odors.  Spa can be used relatively quickly after shocking.  Almost entirely eliminates the use of chlorine.

Cons:  Frequent adding of the shock (recommended to be done each time you use the spa, plus one larger dose once a week).


Chlorine systems use a chlorine-based shock.  The product is added typically one time per week, and possibly other times after heavy spa usage.  The chlorine levels can spike after shocking, so most manufacturers of chlorine shock recommend against using the spa for one hour after adding the shock.

Pros:   Simple to understand.  Any spa can use it.

Cons:  Inability to use the spa after shocking.  Frequent strong chlorine odors after shocking.


Bromine has some ability to not only kill some impurities, but oxidize them to some degree as well.  If using bromine, this can reduce the frequency or amount of chlorine-based shock you need.  But you will still need some at a regular interval.

Pros:   Most spas can use it.  Reduced odors when compared to chlorine.

Cons:  Still need to shock spa at same rate (once per week) compared to chlorine. Spa cannot be used after shocking.


Biguanide systems require a shock treatment as well.  Most recommended routines suggest using a dose of shock one time per week.  Additionally, the use of another product - Stain and Scale Control - is required at the same interval.  Even if your water is not particularly hard, it is recommended you utilize the Stain and Scale Control, since the various combined ingredients needed to make the entire biguanide system effective are often found within the different bottles.

Pros:   Most spas can use it.  Reduced odors after shocking when compared to chlorine.

Cons:  Still need to shock spa at same rate (once per week) compared to chlorine. Two products needed instead of one each week.  Biguanide shock is typically more expensive per bottle than chlorine based shock..

That's it.  Really.  If you follow one of the routines listed above, at the recommended intervals, you will be well on your way to having a hot tub that is continually fresh, clean, and enjoyable.  And the more times you open the spa to find the water inviting, the more times you will be in it - leading to a more enjoyable ownership experience.

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