Shocking, yes again. Sorry.

[96SC]

I know shocking has been addressed about a thousand times (make it 1001).

I got my Taylor test kit today and was reading about shocking.  Then I did a 'search' on shocking and now have a question or maybe two. :-?

How do you shock if you are using chlorine as your sanitizer?

Do you shock with chlorine (dichlor) or non-chlorine (MPS)?  Are you supposed to do a periodic shock with non-chlorine while doing the routine shock with chlorine or the other way around?
 
Am I missing the shock thing altogether?
  
Is it 'dealer's choice', shock however I want as long as it keeps the water 'clean'?


Thanks

[Chad]

You can use either mps(non chlorine shock) or dichlor for shocking. To shock with dichlor you must dose to atleast 10 x the amount of CC. Therefore if your CC is .5 you'd have to add atleast 5ppm. Remember to test for FC 5 - 10 minutes after dosing.

I think most daily dichlor users here including myself shock with mps a couple times a month while supplementing a good superchlorination once a month. This will help keep your CYA level down.

[tony]

You can use either mps(non chlorine shock) or dichlor for shocking. To shock with dichlor you must dose to atleast 10 x the amount of CC. Therefore if your CC is .5 you'd have to add atleast 5ppm. Remember to test for FC 5 - 10 minutes after dosing.

I think most daily dichlor users here including myself shock with mps a couple times a month while supplementing a good superchlorination once a month. This will help keep your CYA level down.

Just to add to Chad's post, if you don't reach "breakpoint chlorination" which is the 10 x CC mark, then you haven't shocked using chlorine.  Non chlorine shock is a little more foolproof in that you just add the required amount for your water volume.  If you under dose, then the product shocks as much as it can.  If you overdose, the remaining product waits until it has something to shock.  The combo method gets you the best of both worlds.

[dax]

You can use either mps(non chlorine shock) or dichlor for shocking. To shock with dichlor you must dose to atleast 10 x the amount of CC. Therefore if your CC is .5 you'd have to add atleast 5ppm. Remember to test for FC 5 - 10 minutes after dosing.

I think most daily dichlor users here including myself shock with mps a couple times a month while supplementing a good superchlorination once a month. This will help keep your CYA level down.

CC = combined chlorine, and FC = free chlorine.  What is CYA?  :-?

[hottubdan]

CC = combined chlorine, and FC = free chlorine.  What is CYA?  :-?

Cyanuric Acid.  

Really shouldn't be an issue if spa is drained 3 or 4 times a year.

[Chad]

If you like to get the most out of your dichlor doses, I'd keep an eye on it. When my CYA hits 100 ppm it takes a much bigger dose of dichlor to do the same amount of sanitizing. My initial fill I hit 100 ppm after just 2.5 months. My next fill was around 3 and know since I shock mainly with mps and use a N2 cartridge, I can get to 4 with no problem. It can go up rather quick if you're not careful and you'll start to waste a good amount of dichlor($).

[Vinny]

I just had a reasonable discussion with a person who is knowlegeable in chemistry at a different website.

With CYA at 20 and a dose of 3 - 4 PPM you can be reasonably assured that the regular bacteria and hot tub itch bacteria will be killed. Using the tub daily, that is a weeks worth of soaking and using dichlor. After that, regular bacteria will be killed but as the CYA goes up the hot tub itch bacteria gets more difficult to kill because the chlorine gets bound to the CYA (as more CYA builds up the more chlorine it will bind up).

After 3 months worth of dichlor use it is almost impossible to kill the hot tub itch even possibly with a shock dose since CYA will be at close or above 300 PPM (again soaking every day and shocking weekly with dichlor). But he pretty much agreed that at 300 PPM CYA even at 4 PPM the regular bacteria will be destroyed; this is the findings that Vermonter had posted a while ago on Doc's site about bacteria.

Actually he suggested not to soak in the tub without chlorine because of the fecal to oral contamination and quite honestly I didn't have an answer for him as I am no where as knowlegeable in microbiology as Vermonter nor that knowledgeable in chemistry as he is. All I could say is that a lot of people use this system (somehow he somewhat knew of this system) and we haven't had a problem yet. As we were discussing this I really was thinking I may be the wrong person discussing this since my lack of knowledge   and was thinking how interesting it would be if Vermonter himself discussed it with him and I could read the outcome but I did my best!

Chad, dichlor puts about 0.9 PPM CYA for every 1 PPM of chlorine. Shocking with only MPS is not a good idea only because if there are resistant bacteria at normal doses the extra chlorine will get them. But it seems you haven't had a problem so maybe it's working for you.

As for shocking, as was said - you need 10x the combined chlorine reading to achieve breakpoint chlorination (TC = FC+CC). You can use MPS but as I said to chad, you may want to hit the tub with extra chlorine to get any really stubborn bacteria.

[sonofsail]

You can also do a partial dump and fill to reduce CYA.  To keep good water clarity, CYA should be at or below 100 ppm.

[Chad]

Vinny, thanks for the info.

Like I said in my previous posts, I shock mainly with mps and once a month I do a superchlorination.