Cleaning a raw water a/c unit

Given that the practice of using spa and pool bromine/chlorine tablets placed in the raw water strainer as a means of cleaning an a/c unit is considered safe by some and it seems to be a common practice, even if one that doesn’t appear to be recommended by manufacturers, I thought I’d do a chemistry experiment to get a little real world data.

There are some interesting youtube videos on the fun you can have with bromine and chlorine, like making bombs when mixing bromine with rubbing alcohol….. bromine bomb - YouTube , creating lightning in a test tube when mixing bromine with aluminum…. BROMINE and ALUMINUM reaction - YouTube , or making a firebomb when chlorine is mixed with brake fluid… Chlorine & Brake Fluid - YouTube .

However, these clearly are extreme compared to the practice described – dropping a couple of pool tabs into the raw water strainer – or asked about by some – metering bromine through the system on a continuous basis. To try to replicate the practice recommended as safe I placed samples of 4 non-ferrous metals with one bromine tab in a pint jar of sea water and a pint jar of fresh water (picture 1).

As expected, the tab in sea water began to produce quite a lot more elemental chlorine gas than fresh water (picture 2, although pretty hard to see in the photo.) I left the metals in the solution for 8 hours, to try to simulate multiple exposures of the metals over time if this practice was adopted as some have advised.

I probably should have sealed the jars to more closely simulate dropping bromine into your raw water strainer but I was concerned the jars might explode from the amount of chlorine gas produced. Probably not likely, but I didn’t want to find out.

The results after 8 hours exposure are shown in the remaining pictures. The results were not as dramatic as I thought but still pretty noticeable. The copper in the sea water got bright within a couple of hours as the patina of oxidation was eaten away, then started to show burning as the bromine continued to work on it. The copper in the fresh water showed some discoloration, but not much (picture 3). The stainless and bronze seems unaffected in both samples (pictures 4.) The aluminum exposed to bromine in sea water reacted much more vigorously than that in fresh water, with more of it eaten away in the salt water (picture 5).

I have no idea how long it would take to cause damage to one’s system by this practice, and that might be a function of how much aluminum or copper is present, but compared to using dilute acid to accomplish the same purpose without the added effect of dissolving copper and aluminum in one's system this “recommendation” doesn’t seem to have much to recommend it after all.

Now I definitely know what substances not to have make contact with my bromine tablets...... Also happy I didn't know about this a kid.....LOL!!

JAT said:

Now I definitely know what substances not to have make contact with my bromine tablets...... Also happy I didn't know about this a kid.....LOL!!

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I seem to remember spending a lot of time as a yoot trying to find things that would blow up as well, but chlorine in brake fluid? Who would have thunk?

Your experiment has nothing to do with reality, and does not duplicate real life conditions. In fact, it is biased to produce a failure to support your point of view. A chlorine or bromine tablet in a strainer is exposed to running water, never reaches a high concentration, and is gone in a day or two and maybe another is added in 1, 2 or three months. After oh, 22 years of doing this, I've never had anything explode, perforate, dissolve or any other negative effects. Does help keep the system clean.

However, if you want to have some fun, take powdered HTH, mix it with Pine-O-Pine and run away. Just don't put that mixture in your strainer.

My hot tubs gone! After just a few days it simply disappeared....

I thought I saw the metal dissolving just moments after the temp reached the perfect 103 deg F....and when I turned my back...poof....the whole thing had simply disappeared because I put some of those evil tablets in there...

Keith said:

Your experiment has nothing to do with reality, and does not duplicate real life conditions. In fact, it is biased to produce a failure to support your point of view. A chlorine or bromine tablet in a strainer is exposed to running water, never reaches a high concentration, and is gone in a day or two and maybe another is added in 1, 2 or three months. After oh, 22 years of doing this, I've never had anything explode, perforate, dissolve or any other negative effects. Does help keep the system clean.

However, if you want to have some fun, take powdered HTH, mix it with Pine-O-Pine and run away. Just don't put that mixture in your strainer.

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The question originally asked was about metering bromine continually into the system, which I thought probably wasn't the best practice given the corrosive properties of bromine which I think is demonstrated. Flowing water continuously would certainly reduce the concentration of bromine in the water passing through the system, but the chemistry causing the corrosion is the same - it just would take longer to have an effect, likely from the fact that as long as the sea water is flowing over the halogen tabs, you're producing chlorine gas bubbles. I'm glad you have never experienced any problems doing this, although some would consider it unwise. Those folks who sued Clorox causing them to discontinue selling Chlorine tabs to keep toilets clean because the product dissolved the metal in their toilets would be some who might disagree. But running water over the tablets wasn't the recommendation that was being offered. What was suggested was dropping a couple of tabs in the strainer for a couple of hours, then turning on the a/c. In other words, exactly what I reproduced. Bromine is marginally soluble in water and once it sits in a closed vessel like a strainer for a couple of hours has probably reached exactly the same concentration as that in my humble experiment.

I couldn't care less what you do to kill algae, Keith. Do whatever you think best. My sole and only point is that if someone asks whether or not to do what has been recommended that clearly is corrosive, why not advise that person to do something that can't damage their system, rather than asserting that a practice not recommended by any manufacturer is the way to go?

psneeld said:

My hot tubs gone! After just a few days it simply disappeared....

I thought I saw the metal dissolving just moments after the temp reached the perfect 103 deg F....and when I turned my back...poof....the whole thing had simply disappeared because I put some of those evil tablets in there...

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You use salt water in your hot tub Mr. Sneed?

Delfin said:

You use salt water in your hot tub Mr. Sneed?

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Sure...I live on a boat...

There are times Mr. Delfin, when it is wise to follow the old bromide that suggests it is better to remain silent ...

RickB said:

There are times Mr. Delfin, when it is wise to follow the old bromide that suggests it is better to remain silent ...

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I 'm sure you 're right Rick. It's frequently best to let closely held myths remain unchallenged by data. No point in upsetting people.

Delfin said:

The question originally asked was about metering bromine continually into the system,

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I don't think so. The question was "does anyone use it " Not about metering it in on a constant basis. Everyone that answered in the positive said that they put a tablet or two in the strainer and ran the unit. Not one said anything about a metering device.

JD said:

I don't think so. The question was "does anyone use it " Not about metering it in on a constant basis. Everyone that answered in the positive said that they put a tablet or two in the strainer and ran the unit. Not one said anything about a metering device.

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It's quite clear folks do it, and as Keith noted, he "does it" by putting the tabs in the water strainer and leaving them there until they dissolve. In other words, he is metering the chemical into his system at the rate the tabs dissolve over "a few days". You have a different process. Rick provided his always helpful data on the metering of bromine for the control of zebra mussels in 1,000 ton + commercial ships. Please carry on, and I ask your forbearance for pointing out that the chemical you introduce into your system also has the capacity to dissolve some of it. Clearly not enough to bother you, but my question remains. Why recommend to someone doing something that isn't recommended by the manufacturers when they do have what they consider safe alternative recommendations to make?

Delfin said:

Rick provided his always helpful data on the metering of bromine for the control of zebra mussels in 1,000 ton + commercial ships.

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Just for the record, the zebra mussel reference was published by the US Army Corps of Engineers and had nothing to do with ships or shipping. It was how to keep locks and dams water systems clear.

Other links I posted were to a university program that used bromine tablets to keep scientific equipment clear of biofouling in sea water.

Another link spoke of using bromine to keep the condensers on a shore based desalinization plant free of biofouling.

But, I guess it is fair to say that the Australian Navy has some vessels over 1000 tons (not very big really, there are plenty of yachts that size) and many more much smaller. Enough that the Navy was interested enough to research the method.

Keep trying though, if you post enough times you might get something right ... the odds of that sort of accident are in your favor.

RickB said:

Just for the record, the zebra mussel reference was published by the US Army Corps of Engineers and had nothing to do with ships or shipping. It was how to keep locks and dams water systems clear.

Other links I posted were to a university program that used bromine tablets to keep scientific equipment clear of biofouling in sea water.

Another link spoke of using bromine to keep the condensers on a shore based desalinization plant free of biofouling.

But, I guess it is fair to say that the Australian Navy has some vessels over 1000 tons (not very big really, there are plenty of yachts that size) and many more much smaller. Enough that the Navy was interested enough to research the method.

Keep trying though, if you post enough times you might get something right ... the odds of that sort of accident are in your favor.

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Having done no more than scan the voluminous and largely irrelevant documents you posted, I only remembered that the use of bromine in these references seemed to be primarily the metering of bromine at around 2 ppm for limited periods of time. Metering was something JD seemed to think no one had mentioned. Except you. But thanks again for your valuable if input, even if it had nothing to do with the topic at hand.

Delfin said:

Metering was something JD seemed to think no one had mentioned. .

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Let's be clear here. JD said "I don't think so. The question was "does anyone use it " Not about metering it in on a constant basis. Everyone that answered in the positive said that they put a tablet or two in the strainer and ran the unit. Not one said anything about a metering device."

This was in answer to your incorrect post "The question originally asked was about metering bromine continually into the system,"

The original question was about using the chemical not the metering of said chemical. I'm not going to read everything all over again but it seemed that most everyone talked about putting a tablet or two into the strainer. Again no mention of metering. Most means almost everyone but in fact may mean someone didn't. Again to be clear.

Keith said:

....... A chlorine or bromine tablet in a strainer is exposed to running water, ...........

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Only when the AC (in this case) is actually running. There is a good chance that it will not be running for hours, perhaps days at a time.

rwidman said:

Only when the AC (in this case) is actually running. There is a good chance that it will not be running for hours, perhaps days at a time.

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Ron,

I'm not sure about how you use your A/C but on mine here in NC the one or two small tablets are only in the strainer for a day to a day and a half. During the time of year I use them the A/C pump runs almost constant for the better part of the day in 80*+ weather. Either one or the other is on if not both at some time.

JD said:

Ron,

I'm not sure about how you use your A/C but on mine here in NC the one or two small tablets are only in the strainer for a day to a day and a half. During the time of year I use them the A/C pump runs almost constant for the better part of the day in 80*+ weather. Either one or the other is on if not both at some time.

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If I'm on the boat in hot weather, the AC runs continuously during the daytime but not often at night. If I'm away from the boat I'll leave it set higher and I suspect it doesn't run as often.

I use no chemicals and have had no problems with growth in the system. Lucky, I guess.

rwidman said:

If I'm on the boat in hot weather, the AC runs continuously during the daytime but not often at night. If I'm away from the boat I'll leave it set higher and I suspect it doesn't run as often.

I use no chemicals and have had no problems with growth in the system. Lucky, I guess.

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Run a tablet through and you may be shocked as to what comes out.

JD said:

Run a tablet through and you may be shocked as to what comes out.

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True dat. Algae, aluminum, copper - all kinds of stuff.

But not to worry. If you can't 'see' what's happening, perhaps it isn't happening at all!

Delfin said:

If you can't 'see' what's happening, perhaps it isn't happening at all!

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Thank you for your valuable contributions to this subject.

JD said:

Run a tablet through and you may be shocked as to what comes out.

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I have water shooting 12" or more out of the AC thruhull.

Here's my plan: When the time come that I have reduced water flow or performance from my AC system, first, I will check and clean the strainer on the intake. If that doesn't correct the problem, I will consult the installation and owners manual that came with the system. I believe it has a troubleshooting section.

rwidman said:

I have water shooting 12" or more out of the AC thruhull.

Here's my plan: When the time come that I have reduced water flow or performance from my AC system, first, I will check and clean the strainer on the intake. If that doesn't correct the problem, I will consult the installation and owners manual that came with the system. I believe it has a troubleshooting section.

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Sounds like a plan to me.

I would use scrubbing bubbles That should do it

I don't know much about the risk from those energetic little bubbles Motion, but you might want to do some homebrew experiments first.

Or, you could just pretend that chemistry and physics don't exist. That's why I smoke three packs of Camels every day. My Grandpa lived to be 90 going through a couple of bags of Bull Durham a day, so I don't hold no truck with those who think smoking might be bad for you. My lungs look fine to me.

Greetings,
OK Mr. Rick B. What is it face-gear-wise here? Underwater, a-la lab or maybe....

It looks like some kind of new design space helmet to me ... might be useful around the a/c overboard after tossing a couple of bromine tabs in the sea strainer though.

RT Firefly said:

Greetings,
OK Mr. Rick B. What is it face-gear-wise here? Underwater, a-la lab or maybe....

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That's for changing messy diapers.