Shocking

[devilwoman]

Just wondering (as I read over Vermonters Style dosing) if you are dosing per your tubs chlorine demand, reaching between 2-3ppm and it is killing all the nasty germs and such after each time you soak...why do you need to Shock?  Sorry if this is such a basic question...

[hottub.pool_boy]

you get an accumulation of combined chlorine over the week and the shock gasses it off.

[Vinny]

There's also the reason of adding a superchlorination if you use chlorine to shock. This gives you the benefit that if the original dose didn't kill everything growing the extra chlorine will do it.

Just remember for the chlorine to get rid of the combined chlorine the free chlorine needs to be 10x the combined amount. Typically I will use MPS if my reading is over 0.5 PPM, I will add 3 PPM chlorine to the tub 20 min after adding the MPS.

[devilwoman]

Vinny why do you use both to Shock?

[Vinny]

If the combined chlorine (CC) is too high I then would need a lot of chlorine and if I want to soak I would soak in what ever level of chlorine. Anything under 0.5 PPM of CC gets hit with 6 PPM of chlorine. Another reason I use chlorine after MPS is I don't want to shock and not have chlorine in the tub any length of time (2+ days).

Enhanced shock contains chlorine and so I figured I could do the same.

[tony]

I do it a little differently.  Because I use a minimal amount of dichlor after use, I like to get my free chlorine level to the 3-5 ppm level once per week.  This would be about 1 tablespn dichlor for my 485 gallons of water.  I shock with 2 tablespns unbuffered MPS when needed.

Used or spent chlorine form chlorimines.  This is what gives a chlorine spa or pool that "chlorine smell".  This is measured by the difference between total chlorine and free chlorine and is called combined chlorine.  Combined chlorine has very little value.  When the combined chlorine level reaches .2 ppm, you must shock to oxidize or vaporize to purge them from your water.  This can be done by quickly raising the free chlorine level to what is called breakpoint chlorination or by adding a sufficient amount of non chlorine shock.   There are advantages and disadvantages to both.  Shocking with chlorine will add to CYA levels and you cannot use the spa until the chlorine level drops, but you get the benefit of a superchlorination.  Non chlorine shock has the advantage of use almost immediately after shocking, but will add to TDS.  It is also more foolproof because if you don't add enough, it still oxidizes what it can..if you add too much, it stays until it can ozidize.  With chlorine shock, if you don't add enough, shocking will not occur and you will have water with a high chlorine level and still have chlorimines.  After shocking, your free chlorine levels should equal your total chlorine level.

[devilwoman]

Tony how long after shocking should both levels be the same?

[devilwoman]

I do it a little differently.  Because I use a minimal amount of dichlor after use, I like to get my free chlorine level to the 3-5 ppm level once per week.  This would be about 1 tablespn dichlor for my 485 gallons of water.  I shock with 2 tablespns unbuffered MPS when needed.

By the phrase "when needed" do you mean when you want to soak right away?  Other wise when do you know when to use MPS or Dichlor for shocking?

Used or spent chlorine form chlorimines.  This is what gives a chlorine spa or pool that "chlorine smell".  This is measured by the difference between total chlorine and free chlorine and is called combined chlorine.  Combined chlorine has very little value.  When the combined chlorine level reaches .2 ppm, you must shock to oxidize or vaporize to purge them from your water.  This can be done by quickly raising the free chlorine level to what is called breakpoint chlorination or by adding a sufficient amount of non chlorine shock.   There are advantages and disadvantages to both.  Shocking with chlorine will add to CYA levels and you cannot use the spa until the chlorine level drops, but you get the benefit of a superchlorination.  Non chlorine shock has the advantage of use almost immediately after shocking, but will add to TDS.  It is also more foolproof because if you don't add enough, it still oxidizes what it can..if you add too much, it stays until it can ozidize.  With chlorine shock, if you don't add enough, shocking will not occur and you will have water with a high chlorine level and still have chlorimines.  After shocking, your free chlorine levels should equal your total chlorine level.

[tony]

After shocking, leave your cover off for about twenty minutes to allow gasses to dissipate.  After that the shock process is complete and you should have no combined chlorine.  To be practical, the next day is a good test if you are concerned.

"When needed" for me is when the combined chlorine level is .2 ppm.  Depending on use, this could be one week or two weeks as a general rule.  Now, .2 ppm is a very small value to determine.  I use a Taylor test kit.  I wait until my free chlorine level is zero.  With the Taylor kit you test for free chlorine first and add drops to test for total chlorine.  Zero gives no color.  If my total chlorine also tests zero (no color), I know I am fine.  If I get any pink, its time to shock.  I check this weekly along with pH.  I check TA monthly.

Hope this all makes sense.

[hymbaw]

Shocking is indeed needed to eliminate chloramines, but that is only valid in a situation using dichlor as your sanitizer.

Whether you use dichlor, bromine, or biguinide systems you need to shock.

If your using chlorine or MPS based shock for dichlor or bromine system, or peroxide for biguinide systems. The primary reason is to eliminate nitrogen based compounds from your tub (sweat, urine, body oils, etc.)

[KarlXII]

'it's all still a mystery to me.
When I shock with a high dosage of chlorine to to oxidize the chloramines, it sounds to me as if I'm just creating new chloramines?  

[tony]

'it's all still a mystery to me.
When I shock with a high dosage of chlorine to to oxidize the chloramines, it sounds to me as if I'm just creating new chloramines?  

Not without something to create them.  Chloraminies are formed by the reaction of free chlorine with ammonia wastes from bathers.  Shocking with chorine raises the chlorine level dramatically in a short period of time.  When free chlorine measures ten time the combined chlorine level, breakpoint chlorination occiurs.  Chloramines are oxidized (explode) and are released as a gas (why you keep your cover off).  Its all just chemistry.

[KarlXII]

Not without something to create them.  Chloraminies are formed by the reaction of free chlorine with ammonia wastes from bathers.  Shocking with chorine raises the chlorine level dramatically in a short period of time.  When free chlorine measures ten time the combined chlorine level, breakpoint chlorination occiurs.  Chloramines are oxidized (explode) and are released as a gas (why you keep your cover off).  Its all just chemistry.

AHA! That explanation did it for me. Thanks.

[anne]

How long should the cover be off?

[Vinny]

I generally leave the cover off 20 minutes when using 6 PPM for shocking and 1 hour if I hit it harder with more chlorine. I'm not that stick with this rule at times but if I have the time (weekends) I try to stick with this.

Regular chlorination, 3 PPM, gets about 5 min or less.