Question About Chlorine Demand

[G-Dub]

I've been following nitro's approach for the past two weeks and my water has never been better...I've been struggling with chlorine demand being between 50 and 75% however, despite frequent shocking to 10-12ppm FC. I also can't seem to get my CC down below 0.5.

As I thought about this system, something about the concept of chlorine demand confuses me...

Chlorine demand is expressed as a percentage of chlorine remaining after 24 hours of non-use of the tub...

Example 1: Day 1, FC 12, Day 2, FC 6. CD = 50%. Amount of chlorine used = 6ppm.

Example 2: Day 1, FC 4, Day 2, FC 2. CD = 50%. Amount of chlorine used = 2ppm.

In both examples the CD is exactly the same, but in example #1 3 times as much chlorine is consumed, in the same tub, in the same time frame.

How do you guys reconcile this? If we just follow chlorine demand, it seems as if it completely depends on what the initital concentration was. Seems to me like Spa #1 is considerably less "healthy" than Spa #2....

[bart6453]

I've been following nitro's approach for the past two weeks and my water has never been better...I've been struggling with chlorine demand being between 50 and 75% however, despite frequent shocking to 10-12ppm FC. I also can't seem to get my CC down below 0.5.

As I thought about this system, something about the concept of chlorine demand confuses me...

Chlorine demand is expressed as a percentage of chlorine remaining after 24 hours of non-use of the tub...

Example 1: Day 1, FC 12, Day 2, FC 6. CD = 50%. Amount of chlorine used = 6ppm.

Example 2: Day 1, FC 4, Day 2, FC 2. CD = 50%. Amount of chlorine used = 2ppm.

In both examples the CD is exactly the same, but in example #1 3 times as much chlorine is consumed, in the same tub, in the same time frame.

How do you guys reconcile this? If we just follow chlorine demand, it seems as if it completely depends on what the initital concentration was. Seems to me like Spa #1 is considerably less "healthy" than Spa #2....

Now that is a damn smart analysis.......Thinking about it....chlorine demand should be expressed in PPM per gallon per day to be totally accurate.

I.E.....500 gallons using 2.5 ppm per day would be .5ppm per 100 gallons per day...or .005 ppm per galon per day.

One could simply go by the 100 gallon mark and have a nice simply number to compare.

But of course...I am a fool so I may be way off course.

[chem geek]

The rate that chlorine reacts with other chemicals and the rate at which it outgasses or breaks down in sunlight (if exposed outdoors) is proportional to its concentration. So that means that the percentage loss is the appropriate thing to measure since twice the concentration of chlorine reacts twice as quickly so uses up twice as much absolute amount of chlorine.

Also, if there are twice as many organics to oxidize, then the chlorine will get used up twice as quickly in percentage terms. So the percentage drop in chlorine is a measure of how much stuff there is that is reacting with chlorine plus some baseline amount that outgasses (again, in percentage terms). If the water is essentially free of organics to oxidize, then the chlorine loss rate is dependent on the "fixed" concentrations of spa surfaces and surface area for outgassing.

As for adjusting for gallons, that depends on how the chlorine is getting used up. If it's from organics in the water, then that's proportional to concentration so percentage is appropriate. If it's outgassing (less with a cover, but still occurs including reaction with hot tub cover), then that depends on the surface area, but typically larger spas are not deeper so the gallon volume and water-to-air surface area are proportional so again it's the concentration of chlorine and therefore percentage loss that is appropriate. Other factors would be depth of the water and temperature which are both the main reasons why even open pools not exposed to sunlight do not lose as much chlorine in percentage terms compared to spas -- lower temperature results in slower reaction time and slower outgassing while the greater depth of water lowers the surface area to volume ratio so that the outgassing plays a smaller role. It is true that for spa surfaces, smaller spas have more spa surface area per volume so any reaction of chlorine with such spa surfaces would be expected to be higher.

The main time that the absolute amount of chlorine usage is relevant is when there is an introduction into the chlorinated water of substances that need to get oxidized by chlorine. If this is a fixed constant amount of introduced substances, then the amount of chlorine loss is directly proportional to the amount of such substances. This is why the rule for the amount of chlorine needed to oxidize bather waste is in absolute chlorine terms independent of spa size (i.e. it's 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock for every person-hour of soaking). The rate of chlorine loss with such an introduction of bather waste starts out high and then slows down, but is complete for practical purposes well within 24 hours (at hot spa temps and assuming the CYA level isn't very high making the active chlorine concentration so low as to take more than 24 hours to oxidize the bather waste -- that's the main reason the water turns dull after a few months of Dichlor-only use).

Richard

[The Pup]

Although I am not the OP, thank you for the explanation...it now makes better sense to me.

[bavol]

combination of chlorine in the form of Hypochlorous Acid (HOCl) and organic wastes (saliva, perspiration, urine) in the form nitrogen or ammonia. Chloramines produce the “chlorine odor” that many people do not like (tear gas is a form of Chloramine). When people complain of “too much” chlorine, it is almost always the case of combined chlorine or chloramines causing the foul odor as opposed to a proper level of Free Available Chlorine (FAC).

But foul chlorine odors are just the ugly mask of the underlying problems present in Spas, Hot tubs & Swimming pool water. Chloramines are the root of many problems in pool water. Chloramines cause problems because of their stability and persistence. This stability and persistence forms additional Chloramines. This is chlorine demand (consumption) at its finest. (Consumers complain that they “just shocked” the pool but there’s no chlorine showing when tested.) As more chlorine is added without reaching breakpoint, more chloramines are formed thereby exacerbating the problem leading to what I’ll call “obvious problems” such as cloudy water or algae growth. testking 646-563 Homeowners and/or pool dealers unfamiliar with chloramines and chlorine demand begin treating the symptoms (cloudy water or algae) rather than dealing with the root cause – especially after the second or third treatment. Without the knowledge of chloramines & chlorine demand, consumers may not receive the help they need. Chlorine demand testing stations aid greatly in determining the appropriate amount of chlorine needed to reach breakpoint chlorination – usually recognized as 10 ppm FAC (free available chlorine) to correct each 0.1ppm of combined chlorine. Failing to realize this amount actually contributes to the chlorine demand problem as more chloramines are formed. testking 1z0-146 We often hear the consumer complain that “my pool guy told me to put in a double dose of shock to treat my cloudy pool.” That amount may indeed fall VERY short of the actual need. When a chlorine demand test is performed, it is often necessary that a dose of 10, 20 or more times of chlorine shock is needed to reach breakpoint chlorination. That means potentially adding 40, 50 or more pounds of shock (in the form of cal hypo) at one time! Yes, at one time! If you try spreading it out (even over a few hours) you’ve defeated the cure and unwittingly added to the problem. We describe the problem this way to our customers in regards to reaching breakpoint or satisfying chlorine demand: Reaching breakpoint chlorination is an “all or nothing” proposition. Think of it as trying to jump the Grand Canyon in a single bound; you can’t “come close”. You MUST reach the other side FIRMLY. You can’t “almost make it.” Whether you’re 2 inches short or 100 feet short, you’re still short. This is where our constant reminding of consumers of the need to weekly “shock” their chlorine or bromine pool. Weekly shocking during the entire time the pool is open & operating will greatly reduce the potential of chlorine demand or consumption. testking JN0-201 In the Spring of 2006 a new, state of the art Chlorine Demand test station (BioGuard®'s Accu-Demand 30) will be available to us. It is virtually 100% accurate. Compared to the old method, results are now available in about 30 minutes rather than 24 hours. This gets the problem rectified immediately, as opposed to waiting an additional day or 2 when the results would be ready and more chloramines form. The Accu-Demand 30 will be the best available method to accurately perform a Chlorine Demand test on the market. If you are one of our “out of town” customers, you can send a water sample for testing. There will be a small fee for this service; however we will call you with the results and recommendations within 3 hours of our receipt of the sample. Please watch for details coming in March 2006.

[The Pup]

[mcw53]

[chem geek]

Yes, delete, because it's spam. I'm not even going to comment on why the 10x rule to get rid of chloramines is wrong.

[quantumchromodynamics]

bavol's post was copied from here, and is not a legitimate post. They only wanted to add links to their website.

[bart6453]

I like spam...spam and eggs...spam and potatoes....cold spam and cheese sandwich.

Spam is made just miles from me....what a wonderful meat.

The meat that won the war in fact.

On the other hand....I dont like spam, I hate spam mail, I hate spam posts...I hate spammers too.

[aschwartz]

combination of chlorine in the form of Hypochlorous Acid (HOCl) and organic wastes (saliva, perspiration, urine) in the form nitrogen or ammonia. Chloramines produce the “chlorine odor” that many people do not like (tear gas is a form of Chloramine). When people complain of “too much” chlorine, it is almost always the case of combined chlorine or chloramines causing the foul odor as opposed to a proper level of Free Available Chlorine (FAC).

But foul chlorine odors are just the ugly mask of the underlying problems present in Spas, Hot tubs & Swimming pool water. Chloramines are the root of many problems in pool water. Chloramines cause problems because of their stability and persistence. This stability and persistence forms additional Chloramines. This is chlorine demand (consumption) at its finest. (Consumers complain that they “just shocked” the pool but there’s no chlorine showing when tested.) As more chlorine is added without reaching breakpoint, more chloramines are formed thereby exacerbating the problem leading to what I’ll call “obvious problems” such as cloudy water or algae growth. testking 646-563 Homeowners and/or pool dealers unfamiliar with chloramines and chlorine demand begin treating the symptoms (cloudy water or algae) rather than dealing with the root cause – especially after the second or third treatment. Without the knowledge of chloramines & chlorine demand, consumers may not receive the help they need. Chlorine demand testing stations aid greatly in determining the appropriate amount of chlorine needed to reach breakpoint chlorination – usually recognized as 10 ppm FAC (free available chlorine) to correct each 0.1ppm of combined chlorine. Failing to realize this amount actually contributes to the chlorine demand problem as more chloramines are formed. testking 1z0-146 We often hear the consumer complain that “my pool guy told me to put in a double dose of shock to treat my cloudy pool.” That amount may indeed fall VERY short of the actual need. When a chlorine demand test is performed, it is often necessary that a dose of 10, 20 or more times of chlorine shock is needed to reach breakpoint chlorination. That means potentially adding 40, 50 or more pounds of shock (in the form of cal hypo) at one time! Yes, at one time! If you try spreading it out (even over a few hours) you’ve defeated the cure and unwittingly added to the problem. We describe the problem this way to our customers in regards to reaching breakpoint or satisfying chlorine demand: Reaching breakpoint chlorination is an “all or nothing” proposition. Think of it as trying to jump the Grand Canyon in a single bound; you can’t “come close”. You MUST reach the other side FIRMLY. You can’t “almost make it.” Whether you’re 2 inches short or 100 feet short, you’re still short. This is where our constant reminding of consumers of the need to weekly “shock” their chlorine or bromine pool. Weekly shocking during the entire time the pool is open & operating will greatly reduce the potential of chlorine demand or consumption. testking JN0-201 In the Spring of 2006 a new, state of the art Chlorine Demand test station (BioGuard®'s Accu-Demand 30) will be available to us. It is virtually 100% accurate. Compared to the old method, results are now available in about 30 minutes rather than 24 hours. This gets the problem rectified immediately, as opposed to waiting an additional day or 2 when the results would be ready and more chloramines form. The Accu-Demand 30 will be the best available method to accurately perform a Chlorine Demand test on the market. If you are one of our “out of town” customers, you can send a water sample for testing. There will be a small fee for this service; however we will call you with the results and recommendations within 3 hours of our receipt of the sample. Please watch for details coming in March 2006.

Most if not all the traditional explainations about Free Available Chlorines, Total Chlorines, Combined Chlorines, chlorine demand, and chloramines has been overlooking the most important factor effecting pool and spa water contamination called biofilm. Scientific research going on at Harvard, Stanford, and especially Montana State University (http://www.erc.montana.edu) over the last 15 years have proven that biofilms absorb chlorine out of solution rendering them ineffective. The more biofilm the more absorption and there is no way to measure the level of biofilm contamination.

Spas at 98 to 101 degrees are prolific biofilm producers. Biofilms exist where ever there is bacteria and a water surface interface or in other words everywhere. This continuing research has also proven that conventional treatment methods discussed in this forum do not penetrate let alone eliminate these biofilms where 99% of the bacteria exist and thrive. There are ungoing studies that show that biofilms are the major source of chloramines. Chloramines are what create the unpleasent smell, bad taste, red eyes, dry skin, and most of the skin irritation.

This occurs because biofilms spread throughout a water body by breaking off in streamers and clusters. If these streamers or clusters have absorbed the chlorine from the solution, which most of them do, the chlorine combined with the organics of the biofilm structure meet the definition of a chloramine. Eliminate biofilm and the chlorimine and/or combined chlorine level becomes much more managable.

The first step to dealing successfully with water management issues is understanding bacterial biofilms and the miultitude of problems they create. For example, the bathtub ring that pools and spas get are a result of biofilms.

[Nitro]

Most if not all the traditional explainations about Free Available Chlorines, Total Chlorines, Combined Chlorines, chlorine demand, and chloramines has been overlooking the most important factor effecting pool and spa water contamination called biofilm. Scientific research going on at Harvard, Stanford, and especially Montana State University (http://www.erc.montana.edu) over the last 15 years have proven that biofilms absorb chlorine out of solution rendering them ineffective. The more biofilm the more absorption and there is no way to measure the level of biofilm contamination.

Spas at 98 to 101 degrees are prolific biofilm producers. Biofilms exist where ever there is bacteria and a water surface interface or in other words everywhere. This continuing research has also proven that conventional treatment methods discussed in this forum do not penetrate let alone eliminate these biofilms where 99% of the bacteria exist and thrive. There are ungoing studies that show that biofilms are the major source of chloramines. Chloramines are what create the unpleasent smell, bad taste, red eyes, dry skin, and most of the skin irritation.

This occurs because biofilms spread throughout a water body by breaking off in streamers and clusters. If these streamers or clusters have absorbed the chlorine from the solution, which most of them do, the chlorine combined with the organics of the biofilm structure meet the definition of a chloramine. Eliminate biofilm and the chlorimine and/or combined chlorine level becomes much more managable.

The first step to dealing successfully with water management issues is understanding bacterial biofilms and the miultitude of problems they create. For example, the bathtub ring that pools and spas get are a result of biofilms.

Allan, I think your only agenda here is to promote you company and sell your product. You still haven't answered my question HERE, which is:

"The consensus here is that biofilm will not form if sanitzer levels are maintained at all times. Are you saying this is not true, and the only way to keep a biofilm free tub is to use your product?"

Until you answer that question, I'll consider your posts nothing more than SPAM.

[The Pup]

I have owned and enjoyed a home spa since the early '70s and have always maintained proper sanitizer levels; this may explain why I do not incur any unpleasant smells, bad tastes, red eyes, dry skin, or skin irritations. I assume I do not have a bio-film issue.