Help with Shocking with Dichlor!!!!!

[green1320]

I shocked my tub yesturday with 2 tbsp of dichlor. The dichlor I am using says it has 56% available chlorine. I took a reading with my Taylor kit 3 hrs after I shocked and FC was 3ppm and TC was greater than 5ppm. When I started before adding the dichlor my Fc was .5 and TC was 1.5 making my cc 1. How long does it take for the shocking process to cut the TC level. Also how long does it take to get back into the tub in a safe zone. Is it normal for the TC level to go up before it goes down or didnt I add enough dichlor to lower this level? Thanks Steve

[green1320]

I have been adding 1 tsp of this dichlor after use and adding 2 tbs to shock. This system is being used with a N2 tube and is how they told me to add chemicals when I contacted them.

[windsurfdog]

If your combined chlorine is indeed 1 ppm (which is rather high), then it would take between 7-10 ppm to achieve the chlorine breakpoint level necessary for oxidation to begin.  That would be around 3 tbsp of dichlor figuring about 1 ppm per teaspoon and 3 teaspoons = 1 tablespoon.  Chlorine breakpoint levels need to be from 7-10 times the combined chlorine level.  Hope this helps... 8-)

[Dr. Spa™ Ret.]

In addition to my windsurffing friends advise, IF you don't add enough chlorine to reach the breakpoint you will only be ADDING to the combined chlorine levels

[hottub.pool_boy]

Free and Total chlorine should be the same. If Total is higher, spa smells like chlorine, burns eyes, etc. Generally, if TC is higher you need to exceed the super oxidation(shock) dosage on the back of the bottle. The amount on the bottle for super oxidation (shock) assumes you have clear water and Free and Toal Chlorine are the same.

[Vinny]

One advice nobody has said yet is if the combined chlorine is high - hit the tub with MPS (non chlorine shock), 15 minutes later you're good to go. If you need some chlorine added at the same time - wait 1 jet cycle and put some chlorine in. Now you have the best of both worlds.

Every so often I get a high combined chlorine level and have to add some extra (more than 4 teaspoons) chlorine. I realized that as I approched a certain level I was getting close to the 2 oz of MPS that I can add without waiting  for the chlorine level to come down - so that's what I do now.

Just remember MPS does not sanitize and will not superdisinfect as chlorine will.

[green1320]

Just checked the tub again. My tc was .5 and tc was 3. Should I shock the tub again or wait one more week. Can you hurt a tub by adding too much dichlor because a couple of times my wife did not know I added it after use and she also added it.  It now has been 30 hrs since I shocked the tub yesturday. Please help me straighten this mess out. Thanks Steve

[Vinny]

Just checked the tub again. My tc was .5 and tc was 3. Should I shock the tub again or wait one more week. Can you hurt a tub by adding too much dichlor because a couple of times my wife did not know I added it after use and she also added it.  It now has been 30 hrs since I shocked the tub yesturday. Please help me straighten this mess out. Thanks Steve

If the 1st tc of 0.5 is free chlorine (fc) then you have a problem if the total chlorine (tc) is at 3 - you have 2.5 PPM of combined chlorine (cc). Hit the tub with MPS to burn up all that cc - you would need to have 25 PPM chlorine to burn it up.

If that figure is really cc then hit the tub with 6 PPM chlorine - 4 teaspoons (?) and the cc will go away.

I may be reading it all wrong - tc= total chlorine; fc = free chlorine and cc = combined chlorine ... usually when you test with drops (I don't know how you're testing) you get the fc and tc readings and subtract fc from the tc to get cc (cc= tc-fc).

[green1320]

How much MPS should I add for 330 gals of water? Also why did the TC level go way up in my tub. Sorry the FC was .5 and the TC was 3. These levels had been about equall for the first two weeks. Am I adding too much dichlor after use? Also when I test for the FC with a taylor k-2005 kit after I add 5 drops of both #1 and #2 then turn upside down to mix do I have to wait to take a reading? I have noticed that the longer I wait maybe 20 sec the darker the solution gets. Then I add the 5 drops of #3 and it gets darker if I add them right away but if it wait about 20 sec before I add the #3 then its about the same color. Thanks Steve

[Vinny]

How much MPS should I add for 330 gals of water? Also why did the TC level go way up in my tub. Sorry the FC was .5 and the TC was 3. These levels had been about equall for the first two weeks. Am I adding too much dichlor after use? Also when I test for the FC with a taylor k-2005 kit after I add 5 drops of both #1 and #2 then turn upside down to mix do I have to wait to take a reading? I have noticed that the longer I wait maybe 20 sec the darker the solution gets. Then I add the 5 drops of #3 and it gets darker if I add them right away but if it wait about 20 sec before I add the #3 then its about the same color. Thanks Steve

To answer your question - I use about 2 oz of MPS for 400 gallons and that's good for up to 500 gallons. It's 1 oz per 250 gallons so 1 1/2 oz should be good for you.

But you should wait until you don't measure any fc so that you can get a true cc reading. At least that's how I do it.  I usually need to add chlorine every other day so I know when that time is that my FC=0 and go from there.

The TC is going up because the CC is rising - if you didn't "break" the used chlorine bond - it just rises. If you truely have 2.5 PPM cc then your chlorine has been busy killing and oxidizing a bunch of stuff and now it's combined with it and needs to be burned off.

What I usually do to test is add my PH and #1 solution to their vials and mix, then add #2 for chlorine and get a reading - 20 seconds seems awfully fast for color darkening. The longer the testing solution is in contact with the test water the darker it becomes ... Take the readings right away for the most accurate measurement. Of course it's kind of hard with adding #3 but it generally is OK.

I use 62% dichlor (dichlor comes in different active strengths) and 1 teaspoon in my tub gives me about 1.5 PPM and I will use 1 teaspoon per person up to 3 teaspoons max (unless there has been a party - doesn't happen too often) so at any given soak I will have 1.5 to 4.5 PPM of chlorine. Your tub has slightly less gallons and if you used the same chlorine (62%) then you would probably be around 2 PPM. My advice is to use measuring spoons and see how much 1 teaspoon gives you - then you know the doses ... 1 Tablespoon = 3 teaspoons = 0.5 oz.