Chlorine tablets in A/C system.

[GoneIsland]

I don't know about using it in an a/c system, but we use bromine tablets in our toilet intake strainer. Works wonderfully for keeping odor down! I think I got the idea from the all knowledgeable Peggy Hall. If she says it's good, I'm good with it

[thinwater]

Originally Posted by a64pilot

Does copper really work? I ask as I have seen bare copper in water and it grows barnacles and "stuff" on it just like everything else.
I believe it used to be that ships were sheathed in copper to keep the worms out of the hull, and that did not work as an antifoul? I think some vessels still have copper sheathed rudders and the like?
We have a member with a Dutch barge I think that has a copper sheathed rudder

Actually, what matters most is whether the copper is bonded to a zinc, and most AC systems do not use zincs. The reason, of course, is that protected parts are not shedding Cu ions. This past year I did a long study of anodes (Zn, AL, none), and more remarkable that the difference in corrosion rates, was the fact that protected surfaces grew a jungle, while non-protected copper stayed clean. There was still some growth on the bare copper, but only a tiny fraction of an inch instead of 3/4-inch.

The interesting corollary is that if you add an anode to the AC system it will start to grow. How much depends on use patterns; with flow it should not grow, and if you close the valves there should be enough Zn ions trapped to inhibit.

In other systems the anode (zinc) serves a similar function.

[jhstacy]

I use the hot tub bromine tablets in my AC as does just about everyone on our dock. I feel/hope they are less dangerous/corrosive than Chlorine and they have done a great job of preventing the AC lines from closing up due to growth.

[buzzstar]

Chlorine tablets, NO! Copper, OK. If copper were not effective (even to the level of being a problem) why are so many places not just controlling its use in paint, and in some instances banning it use, at least in ablative paints (San Diego, California, USA, as one possible example)? As with many things, controlling concentration and delivery method are key factors, and it sounds like several of the contributors above have found methods of delivering the copper that works in their systems, and the methodology should transfer to similar systems. I do not know much about bromine (thought it was very similar to chlorine as far as its activity level) so please do not consider this a weigh in pro or con for that element, although I admit to a intuitive but meaningless con.

[boeing1]

I would not use chlorine, however I do flush my A/C system, I have used saltaway

[Djarraluda]

We use chlorine in 2 areas of air conditioning systems.
1. To sterilise the cooling towers - this is where the algae build-up grows the legionella bacteria, so we pressure wash and sterilise with chlorine regularly as a preventative. This is aggressive and we have very careful control of materials.
2. Where we use sea water cooling to dissipate the heat, a sort-of underwater cooling tower if you like. Draw the sea water in via some screens to keep the major debris out, inject liquid chlorine to kill the growth of everything. We monitor the outlet and adjust the chlorine to get a free-chlorine level at the outlet. This is essential to get the level right, as inadequate levels will not do the biological controls. Sadly, this level of chlorine, with the water basically forms hydrochloric acid and it will chew through copper, harden plastics and strip-off paint around the discharge quite happily. We need to use special plastics, duplex stainless steels or cupro-nickle in lieu of copper (I recommend 70-30, not the cheaper 90-10).

Or to summarise this lot - DO NOT DO IT!
Those who recommend it will probably sell you the replacement parts, or are just doing it to sell you the boat. Good grade copper works well
Roger

[S/V Illusion]

This seems to be a solution in search of a problem.

Normally, when the A/C is off, the system will gravity discharge leaving the internal piping empty down to the WL assuming the seacock is open maintaining water to only the pump and filter which, if installed properly, is also below the WL.

Empty tubing above the WL isn't a place for marine growth to survive. Time to move on?

[a64pilot]

I don't know, but suspect that bottom paint is not just copper powder in paint I suspect the copper is a portion of a chemical compound.
If pure copper was a solution, then I would suspect many people would be adding copper powder to bottom paint, copper isn't that expensive, and I again suspect that pure copper isn't that much of an environmental poison, but that is just speculation on my part.

[JD-Odyssey]

We are liveaboards in Annapolis, MD and our A/C is in constant use for both cooling and heating (until the water temp hits about 40 degrees F). I drop a half tablet (small 1" tablet) into the strainer bowl about twice each summer when the water temp is high and marine growth thrives. The only adverse impact over the past 12 years that we've been doing this is the clear plastic strainer bowl turns cloudy (so, we use the same strainer bowl when we do this). Since we have our two A/C units on continuously, there's always a lot of water passing through the lines and the tablet piece is typically dissolved within 24 hrs. I wouldn't recommend doing this all the time for reasons mentioned by others but we have not experienced any problems doing it infrequently and only when the water temp and conditions warrant it. You may also want to consider the following or in lieu of using any chemicals...

We periodically flush and/or back-flush the A/C lines. We get a lot of fine silt that passes through the strainer and accumulates in the A/C lines as well as some occasional algae growth. Our pier has pretty high water pressure (I use a pressure regulator for our boat shore water connection). We clean the strainer and bowl, disconnect the input line from the seacock and flush the higher pressure pier water through the lines... this usually pushes out a lot of crud. (We do this about two or three times during the summer season.) Occasionally, we will back- flush the lines by connecting the high pressure hose to the line(s) connected to the exiting seacock(s). If you do this, remove the strainer from the strainer bowl so it doesn't trap the crud and allow the water to push the crud out the input seacock (the input seacock can tend to get restricted particularly during summer months when water temps are high). When water temps start coming down, we rarely have to flush the lines. (The silt tends to be less as well as there aren't as many people boating or stirring up the waters at the marina.) I hope this helps...

[capt-couillon]

Chlorine is inherently more reactive than bromine as well as tending to lower ph (acidify) the water it is used in. Not so great on the heat exchanger in the ac. If you really feel a need for a biocide, bromine tablets are a better bet. Lots of folks use them here in the head strainers to eliminate marine growth around the bowl rim and attendant odors.

[GordMay]

Greetings and welcome aboard the CF, JD.