Shocking Question

[SpaNE]

I sanatize with dichlor.  My understanding is that I can shock the spa with dichlor or a non-chlorine oxidizer.  What are the pros/cons of each?

If I use dichlor - how long do you need to wait until the chlorine level drops enough to be safe/comfortable?

Thanks for your help.

[Jacuzzi Jim]

 I like shocking with non chlorinated shock,why double/triple your sanitation levels??
I guess it would depend on how much you use.  As far as waiting that also would depend on how much dichlor you use.

 The method I use if the water gets nasty, 1/2 cup of non chlorinated shock,wait 30 min running pump on low speed,then 1/4 to 1/2 cup chlorine depending on tub size, run pump again.
Add bright n clear run filter pump off and on through out the day if needed.
Check PH/ALK.

That should clean up any mess if you should have one.

Opinions will vary I am sure.

[tony]

I also prefer shocking with non chlorine shock.  It is fool proof.  If you use too much, the residual waits for some thing to oxidize; if you use too little, it oxidizes as much as it can.  You do not have to wait to use your spa.  It is a more complete oxidizer.  The disadvantages are increase in TDS, is more expensive and it does not superchlorinate.

If you shock with chlorine, you must add enough to reach breakpoint chlorination.  If you do not add enough, then you have not shocked.  Shocking with dichlor adds to CYA.  It is probably best to wait until your free chlorine level backs down to 5 ppm to use the spa.  This generally takes about one day, though you certainly could use the spa with 5-10 ppm chlorine if you don't mind it.

[windsurfdog]

I like shocking with non chlorinated shock,why double/triple your sanitation levels??
I guess it would depend on how much you use.  As far as waiting that also would depend on how much dichlor you use.

 The method I use if the water gets nasty, 1/2 cup of non chlorinated shock,wait 30 min running pump on low speed,then 1/4 to 1/2 cup chlorine depending on tub size, run pump again.
Add bright n clear run filter pump off and on through out the day if needed.
Check PH/ALK.

That should clean up any mess if you should have one.

Opinions will vary I am sure.

Jim,

I'm not sure that SpaNE was asking about the worst case scenario that you describe...at least I hope you are describing a worst case scenario...that's WAAAY too much of a "good thing" considering 2 tbsp. = 1 oz. and 8 oz. = 1 cup.  Don't you think that 2-4 tbsp. of MPS or, if combined chlorine is .5 or less, 2-3 tbsp. of dichlor would suffice for a 400-500 gallon tub?

I think if I had a water problem that necessitated the amount of chems you suggested, a water change might be a better solution.

One varied opinion...

[Jacuzzi Jim]

 Thats just my quick fix recipe for people that dont take care of there spas and the water is less than 2 months old.    Hence the word "nasty"

I get a lot of people from other dealers that do not want to help them after the spa has been delivered,also the Costco customers who didnt realize they even had to use chemicals.

 If the water is more than 3 months old I dont bother I tell them to drain and refill,unless they have a slow well in the late summer.

[SpaNE]

I'm not sure that SpaNE was asking about the worst case scenario that you describe...
One varied opinion...

Correct.  I was asking about the best process for a routine weekly shock.

[SpaNE]

I also prefer shocking with non chlorine shock.  It is fool proof.  If you use too much, the residual waits for some thing to oxidize; if you use too little, it oxidizes as much as it can.  You do not have to wait to use your spa.  It is a more complete oxidizer.  The disadvantages are increase in TDS, is more expensive and it does not superchlorinate.

If you shock with chlorine, you must add enough to reach breakpoint chlorination.  If you do not add enough, then you have not shocked.  Shocking with dichlor adds to CYA.  It is probably best to wait until your free chlorine level backs down to 5 ppm to use the spa.  This generally takes about one day, though you certainly could use the spa with 5-10 ppm chlorine if you don't mind it.

Thanks Tony.  Very helpful response.  I think I understood most of what you said, however, I'm not sure what "superchlorinate" means in terms of a disadvantage to shocking with non-chlorine.  I'm also unsure how to interpret breakpoint chlorination.

[windsurfdog]

I'm not sure what "superchlorinate" means in terms of a disadvantage to shocking with non-chlorine.  I'm also unsure how to interpret breakpoint chlorination.

Superchlorination is adding more chlorine than is necessary to maintain 3-5 ppm for normal sanitization purposes.  In my case, using 62% dichlor with a 450 gallon tub, 2 tsp. dichlor will get my ppm up to around 3.  If I measure combined chlorine at .5 ppm or so, I will add enough chlorine to push ppm up to 5-7 ppm in order to meet the chlorine breakpoint for oxidation (shocking) to take place.  The rule of thumb is raising your ppm to 7-10 times the amount of combined chlorine to achieve the chlorine breakpoint.

Personally, I use either MPS or dichlor to shock depending on the situation.  Since MPS contributes to TDS much more than dichlor, I usually lean toward dichlor but I'm very happy to use MPS whenever I want to do a quick shock and be able to soak within the next 24 hours.  Otherwise, I normally shock with dichlor, especially if the tub will not be used for a period of time as when leaving town when superchlorination will keep the tub clean for a period of days without attention.

[SpaNE]

OK...so I normally add 1/3 oz dichlor to my 335 gal tub after a nightly soak.  This generally brings by free chlorine to around 3.

If my total chlorine is 5 and my free is 3, my combined must be 2.  If the rule of thumb is to raise 7-10 times of combined to reach breakpoint - I would need to add about 2 oz of dichlor to shock.  Correct?

I'm assuming that if I add 2 oz it will take at least 2 days before chlorine is back down to 3 again.  Correct?

[svspa]

SpaNE.

I don't think anyone can tell you exactly how long it will take to get back down to 3ppm after a dichlor shock. Each tub and your use of the tub translates into a unique  chlorine demand, which translates to how fast the residual will disperse.

Superchlorination is just an insurance policy. Figure if there are any nasties growing anywhere in the tub your normal daily dose might keep it at bay but a superchlorination will super sanitize your tub and probably kill most anything hanging around. So the added benefit of doing the dichlor shock is you get that 'big kill' to really sanitize the tub.

Steve

[tony]

OK...so I normally add 1/3 oz dichlor to my 335 gal tub after a nightly soak.  This generally brings by free chlorine to around 3.

If my total chlorine is 5 and my free is 3, my combined must be 2.  If the rule of thumb is to raise 7-10 times of combined to reach breakpoint - I would need to add about 2 oz of dichlor to shock.  Correct?

I'm assuming that if I add 2 oz it will take at least 2 days before chlorine is back down to 3 again.  Correct?

A combined chlorine level of 2 is high.  Normally you would shock when your combined chlorine level is >0.2 ppm.  This way if you raise your free chlorine level ot 5-10 ppm you will have exceeded breakpoint chlorination.  Breakpoint chlorination is the process of raising chlorine levels dramatically in a short period of time.  This oxidizes organic matter at a quick rate and results in reduced combined chlorine.  The trick is to be sure you have reached breakpoint dosage which is ten times combined chlorine level.  If you do not reach the desired level, then you have only superchlorinated and have not shocked.

Non chlorine shock does not have the same issue.  It only oxidizes so if you use too little, it will still lower your combined chlorine, just not all the way to zero.  If you add too much, it will hang around and wait for something to oxidize.  From what I have read, it does a more complete job of oxidizing than with chlorine.  Although I shock with non chlorine shock, I like to raise my free chlorine level to +5ppm at least once per month for a scouring effect.

[The_Pa._Lady]

I have a 325 gal tub, how much MPS must I add to superchlorinate?  

I tried using MPS before to shock but I can't get the reading up high enough to superchlorinate.  Then I go back to dichlor to do the job that MPS won't do.

And how much dichlor would you use after each soak to keep the 3-5PPM reading?

Thanks to all.

[hottubdan]

I have a 325 gal tub, how much MPS must I add to superchlorinate?  

I tried using MPS before to shock but I can't get the reading up high enough to superchlorinate.  Then I go back to dichlor to do the job that MPS won't do.

And how much dichlor would you use after each soak to keep the 3-5PPM reading?

Thanks to all.

As stated above, when you use MPS to oxidize you are not superchlorinating.  You will not get a reading showing you have superchlorinated.  To oxidize add about 1 1/4 to 1 1/2 tablespoons MPS.

Don't forget when oxidizing leave the cover open to allow gasses to escape.

[Steve]

Also; Don't attempt to test and adjust pH after superchlorinating as very high readings will alter the look of your pH on your tester (bleach it out).

I always understood breakpoint chlorination as reaching 10ppm. It's interesting to hear otherwise. Regardless of combined chlorines, wouldn't a 10ppm reading acheive this regardless even though you may be taking it slightly higher than need be? I've always taught that it's better to be too high than not high enough when shocking.

As for using the spa afterwards, I always recommend doing this at the end of the day, leaving the cover open for 20-30 minutes and running the jets. Best system I recommend is to use a non-chlorine shock and alternate weekly with a chlorine based shock to superchlorinate.

Steve

[Dr. Spa™ Ret.]

Steve, breakpoint chlorination is achieved when your free chlorine level reaches a point 10 times greater than your combined chlorine level. If you CC is 1.0ppm (or less), then 10 ppm is fine. If it's higher than 1.0 ppm, the 10 ppm of FC wont breakup the CC (in fact, most likely, it will increase the CC levels).