Hello and CYA @ 240-300

[han78216]

Hello everyone. I recently moved to a new house with a pool and I have been reading up this forum and started using BBB method.

The pool, in-ground 25k gallon, water is pretty clear now, but I still get algae on the wall even though I keep chlorine level at above 5ppm all the time.

I recently got the testing kid everyone is recommending and found that CYA is somewhere between 240-300. I had to dilute the water twice. and ph level is 7.5.

Is having CYA@240 the cause of my algae problem? How much water should I replace in order to bring it down to the acceptable level? say 50?

[PoolDoc]

Yes. With CYA=240 ppm, you'd need a MINIMUM chlorine level of 12. If you leave it there, you'll need to dose to about 20-25 ppm 1x per week, and let it drop to 12 before redosing. With a little practice, you'd be able to work out 1x per week dosing.

CYA=240 is a perfectly acceptable level to ME, but not to all the moderators here. Current recommendations are about 50 ppm for general use; 80 ppm for SWCGs, and 150 ppm if you are frequently gone and need to set up 1x per week treatment.

With a 25K gallon pool and CYA=240ppm, you'd need to drain 190/240 x 25K gal, or 19,000 gallons in order to be at 50 ppm when you've refilled. That's what most folks here will tell you do do, and it's what I would have recommended, 2 years ago.

What I currently would recommend is this:
1. Switch to a non-stabilized form of chlorine -- bleach, cal hypo or SWCG (If you need help on sources, let me know)
2. Add borax to the 60 ppm level (24 boxes of 20 Mule Team borax + 7 gallons of muriatic acid)
3. Let your CYA drop over the next few years.
4. Add chlorine 1x per week.

Going that route will give you extremely stable chemistry at very low cost, and you'll only have to dose 1x per week. If you have a sand filter, and use cal hypo -- I'll need to give you special instructions -- you will end up with VERY clear water.

If you do NOT want to switch to a non-stabilized form of chlorine, I'd recommend draining the pool completely since your stabilizer will start to rise as soon as you start adding chlorine.

[han78216]

What's the acceptable level for he chlorine level? Does it depend on CYA level?
We have two young children. I didn't want to raise the chlorine level too high because of them.

Will 12ppm or higher be safe for people to swim in?

[PoolDoc]

Will 12ppm or higher be safe for people to swim in?

Yes. Not "perfectly safe", because nothing is "perfectly safe" -- but the primary risk to your children in the pool, by a VERY large margin, is overexposure to dihydrogen oxide*, rather than overexposure to chlorine.

We'd been reluctant to say yes, for a number of years, even though many of us have swum in pools at 12 ppm or higher. But, this spring, in researching some claims of "chlorine allergies", I found that dermatologists have for years been recommending "bleach baths" at 50 - 100 ppm chlorine with NO stabilizer for patients, including pediatric patients, with eczema and other skin conditions.

Here's that data we have at present:

+ Bleach bath use at 50 - 100 ppm, as a dermatological treatment for both adult and pediatric patients. (Please note: these were naked bleach baths. 100 ppm of chlorine, in the absence of stabilizer, will do serious damage to most women's swimsuits!)

+ Pool Chlor of Arizona and other pool service companies have used chlorine gas to treat 10,000's of home pools since the 1960s in a process that involves stabilizer levels around 150 ppm and chlorine levels that are 15 - 20 ppm at the end of each weekly chlorine injection treatment, but fall to 5 - 10 ppm by the end of the weekly treatment interval.

+ Personal observation #1: In the late 1990's I was servicing a pool in the subdivision where US Congressman Zach Wamp was living. One of the pool staff made unauthorized changes to the feed system resulting in kiddie pool chlorine levels that had been falling, but were in excess of 100 ppm when I arrived, and found the problem. The feed system had been turned off, so levels would have been falling. My best estimate, from talking to the head guard and trying to determine what had happened, was that the changes had been made 3 days before, and corrected 24 hours later. The kiddie pool had been in HEAVY use during this entire period.

What was done was done, so I drained most of the pool into the main pool, and then refilled it, lowering chlorine and stabilizer levels to more typical values. I asked the head guard specifically, but she had had ZERO complaints, even though many infants had used the pool. We'd both seen how simply hearing about a problem would generate complaints ( I did this as an experiment on one pool, years ago, announcing a fictitious problem) and so we said nothing. But I asked to let me know immediately of any complaints that did arise. There were none.

+ Personal observation #2: Around 1998, the Chattanooga Warner Park 50m pool was being used by several USS teams for long course training. I knew a number of the elite swimmers, since many of them worked as guards I serviced, and because my son was a fairly elite younger swimmer at that time. During a one month interval, the pool had some 'control' issues, resulting in OTO 'orange' chlorine levels (20 - 50 ppm) (I wasn't servicing the pool so I couldn't check too closely). Stabilizer levels were very low during this period. The results of swimming in this pool with 20<FC<50 ppm and 0<CYA<20 ppm for 2-3 hours per day, 6 days per week were:
a. loss of all fine body hair
b. dry skin
c. destruction of multiple swimsuits (both guys and girls wore Lycra swim suits)
d. the guys who did NOT wear swim caps had ash-colored hair, with 'goggle-stripes' where the goggle straps protected the hair underneath, which retained it's original color.

+ Personal observation #3: Around 2000, my son was swimming at the McCallie School indoor pool, which experienced similar control problems. I did test this water, but only by dilution, since I did not have the DPD-FAS test at that time. Levels were 15<FC<30 ppm and CYA=0 ppm. This continued for 3 - 4 weeks, until I called the health department. My son, who had moderate to severe asthma, had had NO breathing problem beyond normal, did lose a suit, and did get the stiff, ash-colored hair, but experienced no other ill effects.

+ Analytical observation: Beginning around 2005 (I'll let him comment on this) Chem_Geek took earlier laboratory research and distilled it into an analytical spread sheet that allows calculation of actual HOCl, and -OCl levels, given DPD chlorine levels, pH and CYA levels. Over the past 8 years, both here and at TroubleFreePools, an increasing body of empirical evidence has validated his analytical conclusion that the EFFECTS of chlorine in water are primarily a function of the HOCl and -OCl components. Stabilized chlorine compounds in the water constitute an effective and instantaneously available chlorine RESERVE, but are not themselves active, until the HOCL levels are reduced, allowing the stabilized chlorine compounds to release their 'reserve'.

+ Bureaucratic observation: The US EPA regulates the treatment of potable water by public utilities. Until recently (maybe 12 years ago?) there was NO upper limit on chlorine levels in drinking water. Even today, the upper limit of 4 ppm FC is an ACTION limit. What this means is that the utility is not in trouble, does not have to report a violation to the EPA OR to its customers, but rather simply has to begin to take "ACTION" to lower the chlorine levels. The fact remains, public utilities ROUTINELY provide DRINKING water to some customers that is at or near FC=4ppm, and occasionally provides water at 10 ppm FC . . . and this has not caused any reported problems I am aware of.

+ Literature: I have collected over 8 Gigabytes of peer-reviewed articles on water treatment (and will be publicly indexing them at SwimmingPoolResearch.com, beginning this fall) and have no articles reporting ill health effects on swimmers as a result of chlorine levels that are 10ppm<FC<100ppm. (Those levels do trash hair and swimsuits, as noted above, in the absence of high CYA levels, though I don't have reports on that, either.)

This is probably more than you wanted -- but it's a question that's going to come up as a result of changes in what I'm suggesting. So I took the opportunity to answer your question somewhat more fully than you might have desired.

I'm going to put a copy of this thread in the China Shop, so those that want to continue the technical "Is high chlorine bad for you?" discussion, can do so there, and leave this thread for your personal questions.

*dihydrogen oxide = H2O = water. Overexposure to dihydrogen oxide is more commonly called "drowning". But the observation that H2O is the most dangerous chemical in your pool by far, is absolutely dead on.

[han78216]

Thank you so much for the detailed information. I have been using 6% bleach from Walmart for a month now. I guess I will maintain the chlorine level higher and see if I can reduce CYA level by regular back washing or partially draining pool water.

[han78216]

I did a partial drain and fill on Sat. Now the CYA is around 160.
I added 6% bleach to Chlorine level at 14ppm.

So far it looks pretty good.... And kids are playing in the pool without any complaints.

I might have to do another partial drain because I broke off the pool sweeper connection.
Not sure how to re-pipe under the water.

[chem geek]

+ Analytical observation: Beginning around 2005 (I'll let him comment on this) Chem_Geek took earlier laboratory research and distilled it into an analytical spread sheet that allows calculation of actual HOCl, and -OCl levels, given DPD chlorine levels, pH and CYA levels. Over the past 8 years, both here and at TroubleFreePools, an increasing body of empirical evidence has validated his analytical conclusion that the EFFECTS of chlorine in water are primarily a function of the HOCl and -OCl components. Stabilized chlorine compounds in the water constitute an effective and instantaneously available chlorine RESERVE, but are not themselves active, until the HOCL levels are reduced, allowing the stabilized chlorine compounds to release their 'reserve'.

I moved into a new house that we rebuilt and added a pool in 2003 and used Trichlor pucks in a floating feeder. After one and a half seasons, so halfway through 2004, I started to get an unexplained higher chlorine demand and had a hard time keeping up with the Trichlor pucks, even putting them into the skimmer to dissolve them more quickly (bad to do, but I didn't know that at the time). The water started to turn dull to cloudy. That's when I started looking around for answers and ran into The PoolForum and PoolSolutions where I read about shocking my pool with chlorinating liquid or bleach to kill the algae, getting a proper test kit, checking my CYA level, etc. After lurking for a while, I joined in November, 2004.

I also started to do research to see if I could figure out the chemistry behind the chlorine / CYA chart. I wrote a horribly complex spreadsheet, initially for the saturation index to match the Taylor watergram, but then added the chlorine/CYA equilibrium equations I eventually found that were definitively determined in 1974. I continued to find more and more evidence in scientific peer-reviewed papers in respected journals that this relationship held for pathogen kill times, oxidation rates, ORP levels, etc. The actual algae inhibition levels were determined by Ben through observation. My only contribution for my version of the chart was to "normalize" the values in the table to make them more consistent with the chemical theory.

[BigDave]

Thank you, Richard and Ben, if you haven't heard it, from me, my children, and everyone who's heard you (or swum in the pools of those who have). Your contributions to the community of swimmers and exposition and dissemination of the facts regarding swimming pool sanitization are laudable.