Can't keep Chlorine Levels Up

Algae problems in swimming pool water.
Green (cloudy) water or slimy pool walls.
Black algae. Mustard algae. Pink or white pool mold.

Can't keep Chlorine Levels Up

Postby PeterPap » Mon 09 Oct, 2006 17:13

I have new pool, only 5 months old. It has a salt water system with a Gold Line AquaLine chlorine generator. Everything seemed to be operating properly until about a month ago. All of a sudden, the chlorine level just will not be maintained. It all seemed to start right after I celaned out the filetr and added the DE earth.

Before, I only had the generator set at 40% and the chlorine would be maintained at 2.0 and all was fine. Now, it is set at 90% and the chlorine level will only go to about .5. I have plenty of stabalizer at 110 ppm, the salt is at 3,300 and the ph is at 7.7. Yet, the only way I seem to be able to bring the chlorine level up is to set the generator at super chlorinate. The generator cell is also clean.

The pool company is trying to tell me that it must have some algae. If there is algae, it is completely clear. They also tell me that the chlorine must have bleached the algae and made it virtually invisible. Is this possible? I have brushed the walls and do get a powder. Is this algae or just just dust? This is an area with new homes and lots of construction. Yet, it has been that way ever since the pool was completed. Is the pool company jacking me around or are they just as confused.

Any suggestions?????????????????????????

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Postby Demons1964 » Mon 09 Oct, 2006 19:37

Firstly, when you say "chlorine" are you quoting free chlorine or total chlorine? Combined chlorine + free chlorine = total chlorine. Combined chlorine is weak and ineffective when it comes to sanitization, and high levels of that are indicative of an algal bloom. In which case your free chlorine levels will be low and total chlorine levels high.

Second point of note, your stabilizer level is way too high. You should be aiming for between 30-60ppm. At your level you need somewhere in the vicinity of 8-10ppm free chlorine for complete sanitization. If you do indeed have an algae problem that may explain where it has come from.

Your course of action: Determine first if "combined chlorine" is your problem. I'm not usually an advocate of test strips but in your case it can give you a quick measurement of total chlorine. If total chlorine is greater than free chlorine you'll need to introduce an external form of shock to convert the combine chlorine back to free chlorine.

However, if free chlorine=total chlorine, then clearly chlorine production is your problem. It could be something as simple as a faulty cell sensor restricting current output to the cell. Contact the manfucturer seeing as you'll still be in the warranty period.

As for brushing the walls and seeing a powder what is your calcium hardness and total alkalinity? That may help determine if it is algae or dust.

Can't Keep Chlorine Levels Up

Postby PeterPap » Tue 10 Oct, 2006 08:52

The hardness is at 330 ppm and the alkalinity is at 110 ppm. The test kit I have says the free chlorine and total chlorine are virtually the same. The stabilizer is a bit high but I just did what the pool people asked for me to do. When this first started, the stabilizer was at 55 and they told me to add about 7 lbs of stabilizer. That's what I did.

The only way to get the chlorine level up is to set the control on Super Cholorinate. Setting it at 90% will not raise the cholrine level, but super chlorinate does and will get it up to 5.0 if left on for 24 hours.

The chlorine generator mfg says their equipment is working properly. They made that determination from the info given by the pool company. They say that the cholrine level taken from where the water enters the pool from the pump is at 2.0.

The questions still is can the chlorine bleach out the algae so you can't see it?


Postby Indisgrace » Tue 07 Nov, 2006 06:53

I had the same problem last year, when the chlorine would keep disappearing. If the pool walls feel a little slimy, even though there is no sign of "green", It is possible you have chloramines in the water.
To remove 1 Chloramine atom, it takes 10 Chlorine atoms.
You need to Super Chlorinate...Use 10 times the amount of Chlorine required for a normal "Green Pool" shock dose.
I know it sounds a little weird, but only 1 pool shop out of three was able to give me the solution.
My pool has been fine since.


My kids kept putting the DOG in the pool....I think he was piddling whilst swimming.

The following is an extract from a pool shop advice bulletin board...

Since all chlorinated sanitizers react with water to produce HOCI, chlorine consumption depends on the amount of contamination that is present - not the brand that’s used. Enough sanitizer must be added to meet the chlorine demand of the water before a measurable residual can be maintained. This amount depends on the amount of contamination present in make up water, plus whatever is added by bather loading, rain, dust and other external sources. One particularly troublesome type of contamination is nitrogenous wastes from bathers bodies. Whether they are as simple as ammonia in urine, or as complex as the components in perspiration or saliva, they present special problems when they accumulate in pool water. These contaminants react with HOCI to form compounds called chloramines, or combined chlorine.
The combined chlorine reaction begins with one unit of ammonia, combining with one unit of HOCI to form monochloramine (NH2CI). This reacts with another unit of HOCI to form dichloramine and finally with a third unit of HOCI to produce trichloramine (NCI3). We’re not through yet. It takes a fourth unit of HOCI to finally convert the original molecule of ammonia into harmless nitrogen gas (N2), water and chloride ion (CI-) and a fifth unit of HOCI before a free available chlorine residual can be measured. These chloramines cause plenty of trouble in pool water. Why? Because they are stable and persistent. The monodi and trichloramine from this first unit of ammonia will survive and accumulate with the chloramines formed from subsequent units of ammonia. This is actually chlorine consumption, because HOCI combined with ammonia forms chloramines. Chloramines have very poor sanitizing power, so algae and bacteria can grow. In fact, they have such poor pool sanitizing power that they would be rated at only 0-10 on a relative activity scale with HOCI rated at 10,000. Quite a difference. It’s been estimated that chloramines could provide germ fee water if they were present at a concentration of at least 25 - 50 ppm. But this would create additional problems in a swimming pool, because they’re very pungent and irritating, causing eye irritation and chlorine odors at very low concentrations.
Unfortunately, the chlorine odors generated by chloramines lead many people to think that too much chlorine has been added. So, they stop adding chemicals - and problems grow worse. These symptoms are a signal to test and adjust pH, and add enough chlorine to oxidize all the chloramines, establishing a free available chlorine residual. It’s often very difficult to convince a pool owner that insufficient chlorination is the cause of chlorine odors, eye burn and algae. That’s because she probably tested her pool when a problem was noticed, and got a very positive chlorine test - according to her test kit. This is the most confusing problem caused by combined chlorine: certain test methods measure it as part of a total chlorine residual. If you find a yellow color in the comparator and a clear liquid reagent, then it’s clear that this pool is being tested by the orthotolidine, or OTO method.

I hope this helps

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