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yangcha1

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Jul 8, 2015
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Central Maryland
I have a pool for several years and each year I used the test stripe and add the chemicals by the way of "try and error". From time to time, the pool turned to green. Until recently I followed the instructions of yours, and bought the test kit K2006. For the first time the pool turned to color blue. Thank you. Everything looks fine except the combined chlorine is very high. Is that because I used the "clorox shock plus"?

Yang
 
Welcome to TFP! :wave:

You don't want to add unnecessary chemicals to the pool. Clorox Shock Plus according to this MSDS is 58.2% Dichlor with alum floc and borax or boric acid (some boron salt that isn't explicitly defined). This will raise both FC and CYA so you normally do not want to use it.

This by itself wouldn't raise the Combined Chlorine (CC), but by raising the CYA level you could have too low an FC for that now higher CYA level and something could be growing in your pool. You should post a complete set of test results from your K-2006 and then we can help you.
 
Thank you again. Here is the results by K-2006:
FC:3.5 CC:2.5 PH:7.6 TA:130 CH:170 CYA:70 Salt:4500 Borate:N/A Temperature:84
I have another OTO test kit, then CC is less than 0.5. I don't know which one is correct.

Thanks,

--Yang

- - - Updated - - -

Yes, even since I came across your website, I stopped using Clorox Shock Plus. In fact, it saved me a lot.
 
With your K-2006, you can't go wrong with the powder and drops method to check FC and CC. Remember ... although you have a SWG, your target is 5 based on the CYA of 70. I know 3 is the "minimum", but you don't want to play that card too often or the "algae bug" will get you. :) Do your best to adjust the SWG so you can maintain at 5.

Now having a CC of 2.5 from the Taylor kit is a bit concerning. That means you have an excessive amount of "junk" chlorine still suspended in your water. how does your water look? Is it clear? No signs of algae or anything on the walls or floor? You may want to consider increasing your FC level for a day or two, even if you have to add some liquid bleach. See if that CC gets eliminated. If not, then your next option would be to do an OLCT Pool School - Perform the Overnight FC Loss Test (OCLT) to ensure you don't have active algae/organic material eating your chlorine.

Just some things to keep in mind okay. If you're not sure about this, just let us know.
 
Thank you. So you mean the powder and drops method is accurate? I used to use the test stripe. It is totally nonsense.

The salt level is 4500, because I used this TDS meter:
http://www.amazon.com/HM-Digital-TDS-EZ-Measurement-Resolution/dp/B002C0A7ZY
to estimate the salinity, and it gave result way too low( about half of true value). So I add too much salt into pool until chlorinator reported (salt too high). Intellichlor IC40 does not show salt level but only show low or high. Then I bought Taylor salt test kit and found out it is 4500 -- 4600.

The water looks very clear. I am not sure if algae is on the wall or not, hard to tell. But I will brush it harder. I will follow your advice to shock it and increase the capacity of SWG.

Thanks,

--Yang
 
Yes, the FAS-DPD portion of your Taylor kit (R-0870 powder and R-0871 drops) are the best to use. Test strips are useless. The OTO is simply a very quick "Total chlorine" check, and depending upon your required levels or experience using it, you may not get the best indications of low "free" chlorine. You can use regular liquid bleach (generic is fine) to help assist in raising your FC level a bit (perhaps to FC 9-10) just for a day or so, then check your CC level after that. You want your CC reading to be <=.5 ppm. When it's over .5, we start to get concerned the water needs help.

I didn't see anywhere on this thread your pool specifications (gallons), but if your pool size is 15K or less, then I suggest adding about 1/2 gallon of "regular" liquid bleach in the evening to assist with breaking-down the CC. If you have a pool over 15K, then make it one gallon. That, along with sweeping/scrubbing for a day should be good enough to see if your CC will lower on its own without having to do an OLCT or "SLAM".
 
Thank you for your suggestion. I SLAMed the pool last week. My pool is about 20K. I put 5 gallon of "regular" liquid bleach in the evening and kept circulating, and the water color turned to light blue and very clear. But the CC is still about 2ppm after this and the FC came down to 7ppm next day. I increased CYA a little to about 80 and 90 (maybe too high, I have a salt water pool). Do I need to keep SLAMing until CC is close to zero?

Thanks,

--Yang
 
Hello again Yang. Yes, please keep SLAMming. The changes in your water are good :goodjob:, but you're not finished yet until you pass an OCLT and CC are <=.5. Those are equally important. So keep that FC up at SLAM level, keep the pump circulating, and sweeping. A high CC means the algae is getting killed and in the transition stages of oxidation. That's your trash chlorine. In time we would hope that will get burnt-off and drop below .5.
Also, I would not adjust the CYA any further until you are finished SLAMming. :)

Keep-up the great work!

- - - Updated - - -

Oh, and as a reminder ... if you have a salt water generator (SWG), it should be off during the SLAM to not wear it out. When the time comes for you to perform a Pool School - Perform the Overnight FC Loss Test (OCLT), it needs to be off that night as well.
 

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Thank you again. Yes, I turned off the SWG when I SLAM. When you say "Wear it out", you mean it will damage the cell?

Here is another question, if I have salt water pool, then CYA needs to be high, but according to the SLAM link:

"It is also important that the CYA level not be too high. If CYA is too high cleaning up the pool will take really huge amounts of chlorine and quickly becomes impractical. If a reliable test shows that your CYA level is above 90 you should replace water to bring the CYA level down to 90 or lower before continuing."

This looks like a catch-22. Any sugestions?

Thanks,

--Yang
 
Yes, the higher/steady FC level during a SLAM could cause premature stress or shorten the service life of a cell, so we try to avoid that. :) With a SWG, yes, your CYA must be higher. That's to help it protect and maintain its corresponding FC level efficiently. So you have the convenience of low maintenance FC with little effort required. But because of that high CYA, "if" you ever need to SLAM, then sure, you will use more bleach initially to get to the higher level. But that's why we emphasize to pool owners that once they have a clear, clean pool, to never let their FC drop below their "target". Accidents happen from time to time and we all need to SLAM, but typically, if you keep your FC at or slightly above your target, that won't be a problem.
 
This is the picture of the pool now(the color of image posted here is warmer than the original image) , I will keep shocking it in the weekend.
IMG_1582.jpg

Two questions:

1. Why is the color is not as blue as yours or the pool shown in the frontpage? Is it because of the pool surface or just the water is not good enough?

2. There are white stains on the floor. I tried to scraped it off using brush, but it did not work. I guess the stains are caused by bags of salt which were poured directly into pool by pool guy. Later on I always pre-dissolve then pour into pool. I am not sure if it is the cause, or because of the calcium. I never add well water and always filled by rain. By the way, the pool is 12 years old.


Thank you for your helps!

--Yang
 

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