How To Reduce Cc?

[simonc]

I refilled my tub with new water a few weeks ago. I've been using diclor and now I going to switch to bleach, as per the recommendations of chem geek and nitro.

I bought a Taylor K2006 test kit - just arrived. I tested my spa chemistry (see my values below) and determined that my Combined Chlorine is 1.5-2.0 ppm. Is this too high? The Taylor kit booklet says 0.2ppm can cause irritation. My wife and I aren't experiencing any irritation problems. The water seems fine to me.

My questions are:

1. Do I need to reduce my CC? What is too high for a hot tub or is it just a personal choice?

2. If my CC needs to be reduced, what's the best way? Chlorine Shock or Non-Chlorine Shock?

(Note: If I use Chlorine shock, the Taylor booklet recommends 10 times the CC level which is about 20ppm. "The Pool Calculator" calculates that this is about 12 oz. of 6% bleach for my 275 gallon tub. Seems like a lot to put into the tub all at once???)

Here's the values:

Tub: 275 gallons, my wife and I use it about 4 times/week. Use temp is 104. Drops to ~97 when not in use.

Calcium: 100 (I know it's a little low, but I can only buy the additive in the 4 pound bucket size.)

Alk: 130

pH: 7.4

CYA: 90 (I know it's high, but I don't want to drain water now.)

FC: 1.5

CC: 1.5-2.0

Looking forward to some advice ...

- Simon

[PaulR]

I hear CC higher than 0.5 is worth doing something about.

Non-chlorine shock (monopersulfate or some similar name) registers as CC for a while (on the order of hours, I think) after you add it. If you used that recently then I'd just test again next day and see if the CC is still there.

If you didn't use MPS, or the CC persists, then bring it up to shock level with bleach.

--paulr

[simonc]

I hear CC higher than 0.5 is worth doing something about.

Non-chlorine shock (monopersulfate or some similar name) registers as CC for a while (on the order of hours, I think) after you add it. If you used that recently then I'd just test again next day and see if the CC is still there.

If you didn't use MPS, or the CC persists, then bring it up to shock level with bleach.

--paulr

I'm still confused about using MPS vs. chlorine for reducing CC levels. Currently, I'm not using MPS. So my 2ppm CC value does NOT involve any MPS or other non-chlorine shock in my tub.

Does MPS also reduce CC levels? If so, is there a threshold level that is needed to achieve the desired results? Chlorine shock has a "threshold level":

Desired FC to achieve reduction of CC = 10 times the CC level

According to the Taylor Water Chemistry Booklet (comes with the K2006 test kit), if you don't achieve this minimum level you might actually increase the level of CC instead of decrease it.

Or maybe MPS reduces CCs porportionately, i.e. there is no threshold level: if you add a little MPS the CC will drop a little???

- Simon

[Nitro]

MPS doesn't require a "Threshold". Just add it as needed. Keep in mind MPS will read as CC, even though it actually lowers it.

I'd say check your Chlorine Demand (CD), by shocking to 10ppm then testing FC 24 hours later without using the tub. If CD is above 50%, give your tub a GOOD shock by doing the following:

1. Add 2 cups Clorox Bleach, and 2 oz MPS.

2. Let the jets run for an hour.

3. Measure FC.

4. Cover and let sit overnight.

5. Calculate CD by measuring FC 24 hours later. Compare CD to prior reading.

6. Check pH, and adjust TA if needed.

After this shock you may need to let it sit another day or two before using it, but your water should be like new. The reason your CC (and CD) are high is because you're not using enough Chlorine compared to your CYA. Therefore, I recommend you DOUBLE (you read that right) the amount of Chlorine you add after your soaks. That means if you've been adding 4 oz Bleach after a soak, add 8 oz etc. Until you refill your tub and get CYA down to 30 ppm, you need to use more Chlorine.

Lastly, DO NOT be afraid to add chlorine to your tub. The statement, "Seems like a lot to put into the tub all at once?", is what you need to overcome. The question is not how much Chlorine you ADD to the tub, it's how much Chlorine your tub NEEDS. Give your tub the amount of Chlorine it needs, no matter what the amount is.

[simonc]

The reason your CC (and CD) are high is because you're not using enough Chlorine compared to your CYA.

After doing the shock, I plan on doing a partial drain/refill of my tub to try to bring the CYA level down to about 40-50ppm. Getting to 30ppm with my Taylor K-2006 test kit seems to me to be difficult since the minimum test result is 30. Maybe I'll get lucky and get near that???

The next time (hopefully, at least few months from now) that I do a complete drain/refill of my tub, I think I'll to hit the 30ppm CYA level by adding CYA stabilizer to the proper level and then start using bleach directly. The pool calculator you recommended calculates the needed quantity. (My brother has a pool at this house so he's got a bunch of the CYA stuff.)

Thanks for the advice.

- Simon

[Nitro]

After doing the shock, I plan on doing a partial drain/refill of my tub to try to bring the CYA level down to about 40-50ppm. Getting to 30ppm with my Taylor K-2006 test kit seems to me to be difficult since the minimum test result is 30. Maybe I'll get lucky and get near that???

It's not difficult at all. Just raise CYA until you can't see the black dot at 30 ppm. Simple!

I wouldn't bother doing a refill unless you do a full one. I'd just wait a month, and do a full refill before the winter. Just my opinion, but it's up to you.

[BigDfromTN]

MPS doesn't require a "Threshold". Just add it as needed. Keep in mind MPS will read as CC, even though it actually lowers it.

I'd say check your Chlorine Demand (CD), by shocking to 10ppm then testing FC 24 hours later without using the tub. If CD is above 50%, give your tub a GOOD shock by doing the following:

1. Add 2 cups Clorox Bleach, and 2 oz MPS.

2. Let the jets run for an hour.

3. Measure FC.

4. Cover and let sit overnight.

5. Calculate CD by measuring FC 24 hours later. Compare CD to prior reading.

6. Check pH, and adjust TA if needed.

After this shock you may need to let it sit another day or two before using it, but your water should be like new. The reason your CC (and CD) are high is because you're not using enough Chlorine compared to your CYA. Therefore, I recommend you DOUBLE (you read that right) the amount of Chlorine you add after your soaks. That means if you've been adding 4 oz Bleach after a soak, add 8 oz etc. Until you refill your tub and get CYA down to 30 ppm, you need to use more Chlorine.

Lastly, DO NOT be afraid to add chlorine to your tub. The statement, "Seems like a lot to put into the tub all at once?", is what you need to overcome. The question is not how much Chlorine you ADD to the tub, it's how much Chlorine your tub NEEDS. Give your tub the amount of Chlorine it needs, no matter what the amount is.

SimonC,

Read and re-read this. I am a newbie here and was having some of the same problems.

I was concerned about how much bleach I was using at one time and it was gone in 24 hrs. I was using 16-24 ounces a day. Finally re read Nitros info and used the MPS and bleach. The chlorine levels stayed high for 2 days but FC and TC levels are good now. Soaked last night with wife and added 8 ounces and its still reading high this AM. Hopefully by late tonight when we can soak again it will be back down to 3-5 range and I will adjust my bleach adding as needed.

I too was getting frustrated. Dont be afraid of putting "too much" bleach.

Finally seeing some light at the end of the newbie learning water chemistry tunnel!!!

[PaulR]

The next time (hopefully, at least few months from now) that I do a complete drain/refill of my tub, I think I'll to hit the 30ppm CYA level by adding CYA stabilizer to the proper level and then start using bleach directly. The pool calculator you recommended calculates the needed quantity. (My brother has a pool at this house so he's got a bunch of the CYA stuff.)

The amounts of straight CYA you need in a hot tub are pretty small, on the order of an ounce or two. Many people use the dichlor-then-bleach procedure outlined in "Nitro's approach to water maintenance" (see link in his post above). It's pretty reliable.

--paulr

[Nitro]

SimonC,

Read and re-read this. I am a newbie here and was having some of the same problems.

I was concerned about how much bleach I was using at one time and it was gone in 24 hrs. I was using 16-24 ounces a day. Finally re read Nitros info and used the MPS and bleach. The chlorine levels stayed high for 2 days but FC and TC levels are good now. Soaked last night with wife and added 8 ounces and its still reading high this AM. Hopefully by late tonight when we can soak again it will be back down to 3-5 range and I will adjust my bleach adding as needed.

I too was getting frustrated. Dont be afraid of putting "too much" bleach.

Finally seeing some light at the end of the newbie learning water chemistry tunnel!!!

Just FYI, you could have done the same thing with just bleach (no MPS). You just would have had to add more bleach (3-4 cups, a super shock). I suggest MPS in addition bleach, because it really helps out the oxidation process. I still want to make the point, don't be afraid to use too much Chlorine.

Check out my link below about Chlorine Demand (CD). You should never let your Idle CD get too much above 50%. If you keep CD low, you'll have a lot less problems.