very high CC level

[tmtklt]

Hi guys, I really need some advice...so, let me fill you in on what's been going on with my pool. About 3 weeks ago, we got a lot of rain and my yard overflowed into my pool. I think we got about 10" of rain in 3 days. The night that my pool flooded it started at 10:30 pm and I could see dirt and debris from the yard filtering into the pool. By the time I woke up the next morning, my pool was green, but I could still see the bottom a little. Yuck. I didnt have a good test kit then, but do now. I pumped the excess water off the pool and started to rebalance the pool. The salt level was very low and I had no chlorine. I added salt so the generator could start producing chlorine. I also added a bag of aqua chem plus (sodium dichloro-s-triazinetrione 58%). I used 3 total. (please dont fuss) The pool was clear within two days. I got the leslie's test kit that tests dpd chlorine (did not have powder) and discovered that I had a big difference in free chlorine and total chlorine. A few weeks later I got the supplemental fas dpd test kit (the one that does just that one thing) from yall and I was very surprised to learn that my FC was .5 and my CC was 5.

I dont understand why the CC level is 5 when the water is clear. My other test parameters were okay...ph 7.6, TA 90, CH 250, CYA 40 and salt 3200 water temp is about 59. (12/27/2009)

I've started to shock the pool with bleach. I used the calculator to help me figure out how to get the FC level up to about 20. I think I've added about 8 jugs of bleach over the course 6 hours starting yesterday evening at 4:30 pm. (I checked hourly from 4:30 to 10:30 pm last night and It says 6% and their 96 oz jugs.) And I've also got the SWCG on super chlorinate. FC is 20, CC is 9, ph was very high and I've added 1/2 a gallon to reduce it to 7.5 (I'm out of acid now), TA is 120. I have not tested the CH or CYA today. I'm out of the CYA reagent.

So, I dont understand why the CC level went up and why isn't it falling yet? Any ideas? Thanks for any help.

 

[tmtklt]

an update...as of 11:15 am my FC is 21.5 and CC is 7. The CC level is starting to come down a bit and I've not added any liquid bleach to the pool since last night. (the SWCG is on superchlorinate and is making chlorine thus, the increase of 1.5 ppm). Maybe I have not yet reached breakpoint chlorination, but I might be on the verge of it since the CC has come down from 9 ppm. I've got another 8 jugs of chlorine in case I need to add more.

We did have a big pool party back in mid september with 6 kids plus several adults, then the 10" + rain that flooded my yard (I've got two labradors and I was not able to pick up the piles of love before the yard flooded into the pool) that's probably where all the cooties have come from. Plus, I bet some of every chemical (fertilizer, lime, bug stuff - I put all those out in October) that everyone uphill from me has put in their yard and from my yard has been introduced into the pool from the 10" + of rain we got the 2nd week in Dec.

I'm tempted to add more bleach since the CC is starting to come down. any suggestions?

Thanks for reading this far and especially since its a holiday!

 

[chem geek]

Happy New Year!

The dirt from your yard has lots of organic material in it which chlorine reacts with and that is the source of the Combined Chlorine (CC) reading. Unlike the simpler compounds in your sweat and urine, such as ammonia and urea, soil contains more complex organics that take longer to oxidize. So maintaining a shock FC level will speed up this process of getting rid of the CC, though it may take quite some time (i.e. days to weeks depending on the substance). Also, I presume your pool's water temperature is fairly cool and that will slow all chemical reactions way down so pool owner patience is needed. You will probably need to turn down your SWG since the chlorine probably won't be dropping due to the low temps, unless you've still got direct sunlight on your pool.

Forget about "breakpoint chlorination". It doesn't work that way. That term only applies to adding chlorine to ammonia in a scenario where you don't have measurable FC (only CC, until enough chlorine is added to the ammonia). In your case, the reactions are just slow, but there is no "break" when things will suddenly work; the CC will just slowly decline and will take somewhat longer to decline as the CC gets lower.

Richard

 

[tmtklt]

Thanks for your reply. I did get a little impatient and added another 3 jugs of chlorine...so now my FC is 27 and the CCs are 4. I also forgot to mention that I've got a huge flower bed that only had organic peat and mulch in it. I'm sure some of it washed into the pool when the yard flooded. I really appreciate your help. I think if I can maintain this level it will come down pretty quick. I needed to see that change starting to take place. Another question, provided that a pool has no CC's, about how much FC will a jug of bleach typically add? And is there a formula that I could possibly use to guess how many gallons my pool holds by measuring a chemical change?

 

[chem geek]

You should also be cleaning your filter assuming that some of the material is able to get filtered out. There's no sense in trying to oxidize everything that is caught in the filter since physical removal would be much faster. If you get impatient and don't care about spending more money, then using a coagulant/clarifier would collect more particles so they get caught in the filter more readily, but that's not normally needed nor recommended.

You can use The Pool Calculator to calculate dosages -- both ways. So you can figure how much bleach it takes to achieve a certain FC for a given pool size or you can go to the bottom of the page in the "Effects of adding chemicals" section to see the FC rise for a certain amount of bleach with a given pool size (entered at the top of the page).

For a 13,000 gallon pool, a 96 ounce (3/4 gallon) jug of 6% bleach will increase the FC by 3.6 ppm. So 3 jugs would normally raise the FC by 10.8 ppm. So either some of your FC is getting consumed or your pool water volume is larger than you think -- it's probably more of the former. Note also the assumption of 6% bleach, such as Clorox Regular or most off-brand Ultra bleaches. If you are using an off-brand Regular bleach, this is often very weak at 3% or less.

 

[geekgranny]

You should also be cleaning your filter assuming that some of the material is able to get filtered out. There's no sense in trying to oxidize everything that is caught in the filter since physical removal would be much faster.

Did you vacuum the pool well? Any gunk left in the pool (and filter) will continue to cause chlorine consumption. I used to get a couple, or more, floods into the pool from "frog choker" rains, a few times a year, until I put sandbags around to prevent that. We are also a few feet lower on the hill than most of the houses. As more houses have been built, over the years, more and more silt and all the "poisons" used, up the hill, make it to our "green" environment. Might want to get some sand and bags for a temporary solution until you can figure out a more permanent way to prevent it.

I've actually had some of the bags in places for several years now. (I initially used 3.5 tons of sand .... little ol me doing all the work. ) I've collected enough silt in a couple of years to build a bed in front of the bags, along a 30 ft section, for planting ground cover which will grow over the exposed side of bag too. Another thing to do, if you want a semi-permanent sand bag dyke is to cover the bags with Coolaroo fabric, that blends with your landscaping, and prevents UV breakdown of bags.

BTW... in several areas, where I have the bags, we have old and ancient trees. Digging trenches would disturb the roots too much and kill the trees. Soon after we moved in we lost a 150 yr old oak, that was about 10 ft from pool that had been put in 5 years earlier, and several Ashes even closer to pool, between the pool and house. They actually poured the decking around the Ashes with tree wells in the decking. The tree doctor said the death of the oak was very likely caused by the installation of the pool. The Ashes were pretty old and nearing the end of their lives but the pool installation probably accelerated their deaths too.

gg=alice

 

[tmtklt]

Y'all the pool is clear and has been clear since 3 days after the yard flooded. That's why I didn't understand the high CCs if the pool was clear. As of 4:45 pm the FC is 28, CC is 1 (might be a little less because 1 drop was almost clear, but not all the way) and ph is 7.2. I'm having trouble testing the TA, and CH (I assume due to high chlorine level) but the CYA is 40.

We did not clean the filter after the yard flooded. There's no debris on the pool floor, except for occasional grass and the pool cleaner picks that up. Its a huge cartridge filter and I'm not sure I can get it back together by myself. My hubby is out of town...and the filter is only 5 psi higher than when we cleaned it in late September.

Assuming I can maintain this level until the CCs are gone, how do I get rid of all that chlorine?

The SWCG is off and will not produce anymore chlorine since the water temp is 51 degrees and will probably not get any warmer since we're forecast to have lows in the 20s next week.

 

[JasonLion]

If you got some fertilizer, or any of several other chemicals, in the pool you can have exactly the symptoms you describe, high CC levels and clear water. This state can persist for a while, until all of the fertilizer (or whatever) is burned off.

The only solution is to continue adding chlorine up to shock level until the CC level goes down to zero.

It is possible to get an rough estimate the total amount of chlorine you will need by testing a small sample of pool water in a bucket and seeing how much chlorine it takes to clear the CC in the bucket. I wouldn't normally bother doing that test in this situation, but some people like the peace of mind of having an estimate.

 

[chem geek]

As for getting your chlorine lower after the CC has gone down, you could just let it ride as it will slowly drop over time. If you wanted to swim (assuming the water isn't really cold) or you wanted to drop the chlorine faster, then you could use a chlorine neutralizer (sodium thiosulfate) if you don't have any direct sunlight.