Considerations & Suggestions

Shocking a spa or hot tub  refers to the application of large quantities of chlorine, non-chlorine shock or hydrogen peroxide.  Typically 5-10 times the normal dose is used, based upon actual conditions and needs.  The purpose of this large dose is to break down the combined chlorine, organic waste and contamination and re-establish a positive level of sanitizer.  Shock treatments must be repeated, until such time as a stable sanitizer reading can be achieved, for at least a few hours.  Products such as sodium dichlor and non-chlorine shock are used for this purpose, with spas utilizing chlorine, bromine, ozone generators, ultraviolet sanitizers, mineral sanitizers or ionizers.  These products cannot be used in a biguanide-maintained spa:  only concentrated hydrogen peroxide can be used as the shock.  A spa should be shocked at the first signs of algae or slime, after periods of heavy bather usage and at the onset of a loss of water clarity or quality.  Another common practice is to shock treat the spa water every week, typically, after a period of high bather usage. This will help to re-establish the sanitizer level, help prevent the growth of resistant microorganisms and help maintain sparkling, crystal clear spa water.  Clicking on the underlined and highlighted "keywords" or "catch phrases," in the archived answers will give you access to additional information on that topic or product.  Please refer to the Glossary, if there are terms or phrases that require explanation.

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► Chlorine Shock And Bromine?

If I am using Bromine, should I use a non-chlorine shock treatment and would anything negative happen if I used a chlorine shock?  This past summer, I only used non-chlorine shock and had beautiful water.  Last week, the pool dealership gave me a fast-shock that has chlorine in it.  Is it safe to use with Bromine or not?  Thanks.

Christine, 5/13/2007

Using the chlorine shock should not be a problem.  When you add a non-chlorine shock to bromine maintained water it destroys contamination or converts into bromine.  Guess what?  The same thing will happen, if you use chlorine.  It all ends up as bromine.  Isn't chemistry great!  I assume that the product is sodium dichlor and it should provide equally good results.  There would not be a problem switching back at any time.  Enjoy the spa.

Sincerely.  Alan Schuster, 5/13/2007

► Something Other Than MPS?

I think I'm allergic to non-chlorine shock and my wife doesn't want to use chlorine in our indoor spa because of the odor. Can I use a Bromine system and shock with something other than mps?  Or what else would you suggest?  Thanks.

Hal F., 2/3/2009

If you are maintaining your spa on bromine, excess mps will convert to bromine.  You can shock with chlorine.  There should be little persistent chlorine odor, as it will be converted into bromine.  I am not sure if your are allergic or not.  The problem may be rooted in poor sanitation and not have anything to do with bromine or mps.  I certainly agree that avoiding chlorine would be best, in terms of the odor.  What I suggest is that you add an ozonator.  This will allow you to avoiding using shock, under normal conditions.  In addition to the ozonator, you should maintain a 1-3 PPM level of bromine and use a mineral sanitizer, to help maintain this lower level of bromine.  Either way you should get better water quality with less odor and fewer chemicals being added.  I hope that I have been helpful.  Good luck and enjoy the spa.

Sincerely.  Alan Schuster, 2/3/2009

► How Often To Shock?

My spa is maintained with granular dichlor.  Do I still have to shock the water? 

Henry D., Statesboro, GA, 12/3/2003

Shocking helps to destroy organic byproducts and wastes and helps prevent the development of resistant microorganisms.   Shock treating the spa water, once a week or at the first signs of a loss of water quality, is a reasonable minimum.  You could use the same dichlor product to shock:  just add a double or triple dose.  I would prefer to use a non-chlorine shock.  This product will help destroy the odorous chloramines and get you back into the spa even sooner.  If your spa is equipped with an ozonator, the need to shock treat a spa can be reduced, especially if the ozonator is run off a separate low-speed pump.  I hope that I have been helpful.

Sincerely.  Alan Schuster, 12/3/2003

► To Shock Or Not To Shock?

Thanks for your web site, I find it very helpful.  I have a spa that is 300 gallons.  I run 6 days a week and get in the hot tub after my run.  This obviously takes its toll on the water chemistry.  Do you have any suggestions as to how often I should shock and how often I should change the water?  Any thing else you think I should consider?

Hughes J., 6/11/2004

If you don't have an ozone generator, get one!  All that activity is going to add a lot of wastes to the water.  Ozone can rid the water of the wastes and byproducts, without greatly adding to the dissolved chemical load.  Make sure that the ozonator is run for extended periods of time after each use.  Doing this could help reduce the need frequent shock treatment.  However, a weekly shock treatment is still useful to rid the water of wastes and help prevent the development of sanitizer-resistant microorganisms.  How often to change the water can be subjective.  The only scientific way would be to measure the TDS.  If it rises 1500 PPM above the starting point, without a doubt the water should be changed.  Every 3 months is a common guideline, but heavy use could mean more frequent changes.  A lot depends upon the sanitizer being used.  Some methods add a lot to the TDS.  Ozonation does not.  The important thing to do is maintain the water chemistry and clarity and it is the best indication of water quality.  I hope that I have been helpful.

Sincerely.  Alan Schuster, 6/11/2004

► Is Shocking Necessary?

Why do I need to shock my spa when it has an ozonator and I add chlorine daily?

Bill G., 2/16/2007

You may not have to.  But, that doesn't mean that you shouldn't!  Once in a while it is a good practice to shock the spa, in order to not only destroy organic contamination, but to eliminate microorganisms that might have able to survive more typical chlorine levels.  There is no set rule and every spa is different.  If the spa is not going to be used for a few days, that is always a good time, as it will not interfere with the use of the spa.  You can further reduce the need to shock, by adding a mineral sanitizer, such as the SPA FROG.  I hope that this information is helpful.

Sincerely.  Alan Schuster, 2/16/2007

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► Choosing A Spa?

► Hydrogen Peroxide?

I have an Ionization unit and the dealer recommended that I use a non-chlorine shock on a weekly basis.  It there a specific reason that I can't use a chlorine shock?  Thank you.

Tim W., 5/6/2004

Most people use an Ionizer to avoid the odors associated with chlorine.  Using a chlorine shock could create some of those chlorine odors.  Using a non-chlorine should help avoid odors and give you all the benefits of a shock treatment.  It is possible that the Ionizer's manufacturer has another reason: check the owner's manual to be sure.  I hope that I have been of assistance.

Sincerely.  Alan Schuster, 5/6/2004

Can a non-chlorine shock be used in a spa being maintained with biguanide?  I use hydrogen peroxide now, but would like to use something else.  Thanks.

Matt, 8/1/2003

Non-chlorine shock is potassium peroxymonosulfate.  It cannot be used with biguanide as a spa shock treatment or for any other reason.  Non-chlorine shock will chemically destroy the biguanide. Hydrogen peroxide is the product of choice.  Enjoy the spa experience!

Sincerely.  Alan Schuster, 8/1/2003

► Using Chlorine Or Non-Chlorine Shock?

Thank you for your informative website. I am a new spa owner and have decided to go with sodium dichlor, as a sanitizer.  But, after reading a lot on the internet, I'm still confused.  Should I use a chlorine or non chlorine shock with this?  Why would I choose one over the other?  I guess I just don't get the difference, especially when using chlorine as the sanitizer.  Thank you for your time.

Evan W., Tucson, AZ, 11/14/2007

You can use either one.  The purpose is to maintain a free chlorine level of 1-3 PPM, with the total chlorine not more than 1 PPM higher.  If the total chlorine gets to be too high, the non-chlorine might do a better job of narrowing the difference.  If you add the SPA FROG, you will be able to maintain proper conditions, while adding less chlorine.  This mineral sanitizer uses silver ions to provide persistent sanitizing action, reducing the chlorine usage and chemical presence.   I hope that you will find this information helpful.

Sincerely,  Alan Schuster, 11/14/2007

► When To Shock?

Theresa, Ontario, Canada, 10/18/2003

You can shock treat your spa, as often as needed, to maintain a 3-5 PPM level of bromine.  Shock treating merely refers to the addition of a quick dissolving product that will provide an instant boost to the bromine level of the spa water.  You can use the current product or sodium dichlor or a non-chlorine shock for this purpose.  The bromine product is slow dissolving and the easiest way to boost the level is to add "shock."  I hope that I have been helpful.

Sincerely.  Alan Schuster, 10/19/2003

► Too Much Shock?

Kristin W., 1/19/2004

Not really!  An ideal bromine reading should be 3-5 PPM.  Higher levels could be irritating.  If the water was "perfect"  adding shock would have boosted the bromine level.  The water being in good condition probably did not have a lot of wastes and byproducts present that would react with bromine.  It may take a few days for the levels to drop and I would not recommend bathing, unless you know how high is high.  In the future, remember you can always add more - you can't take out!  Add shock treatment in increments until the level is 5-10 PPM, instead of adding a fixed amount and, possibly, overdosing.  If you want to lower the level quickly, many dealers carry a chlorine/bromine neutralizer product.  Follow directions and add it increments.  Your pH is too high and should be lowered to the 7.2-7.8 range.  I hope that the information proves helpful.

I am using bromine tablets in my hot tub.  I work hard at keep the level in the 3-5 PPM and the water seems to be in excellent shape.  Do I still need to shock?

Bob, Tiburon, CA, 12/2/2003

Good question!  If you add a spa shock treatment, such as a non-chlorine shock, on a weekly basis or after heavy bather usage or at the first signs of a loss of water quality, you will help destroy the buildup of organic byproducts and help prevent the development of resistant microorganisms.   On the other hand, if you rarely shock the water, you increase the likelihood of organic byproducts building up and the development of resistant microorganisms.  At the very least, consider adding some non-chlorine shock after periods of heavy usage, in order to quickly re-established the bromine level.  I hope that I have been helpful.

Sincerely.  Alan Schuster, 12/2/2003

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