Refrigeration & AC: Chlorine vs Bromine

[Lucky Chucky]

Captains,

I just attended a seminar on Marine Refrigeration & Air Conditioning at the Puerto Vallarta Yacht Club.

Scott Power gave a 2 hour presentation and discussed the issues of clogged plumbing in the sea water pumps and lines to the refrigeration and AC units.

He recommended a regular scheduled fresh water flush...and discussed that he's seen some yacht owners putting Chlorine tablets for swimming pools in the strainers.

With a smile, he said that he couldn't officially recommend that but he knows a lot of owners here in the tropics that swear by it.

Another chap in the audience piped in that he swears by Bromine tables used in hot water spas.

Any thoughts on this matter that you'd like to share?

~Lucky Chucky
mv Ho'okipa
S4326

 

[JohnEasley]

I've heard anecdotal evidence that Chlorine was too harsh for some of the more delicate components. We've been using Bromine tablets for a while now. Mostly, we drop them in our shower sumps and the lowest point in the bilge.
For the a/c strainer, we have adopted a different approach that seems to be working well. In the warm Florida waters, the a/c strainer basket would have an 1/8" of growth and slime around the outside of the basket in a week's time. We close the seacock, remove the basket, place it in a cheap 24 oz drink cup from a fast food restaurant, fill the cup with bleach, and let it sit on the dock for about an hour. Then we rinse everything and put the basket back in. There is something about the residual bleach on the basket, even after thoroughly rinsing, that seems to retard slime growth and critters. Now, we barely have anything on or in the basket after a week. It also helps to pick up a second basket so you can close the seacock, pop open the strainer, swap the baskets, reopen the seacock and you're back in business. Then follow the same hour-long bleach soak process for the old basket. Works great with no Chlorine or Bromide tablets in the strainer at all.


John

 

[Lucky Chucky]

Thank you for the post John.

I've decided to try the Bromine tablets in the strainers for the AC & Refrigeration units.

I'm still cogitating on your idea of putting them in the sump and bilges...

~LC

 

[CaptTom]

Thank you for the post John.

I've decided to try the Bromine tablets in the strainers for the AC & Refrigeration units.

I'm still cogitating on your idea of putting them in the sump and bilges.

I'd like to hear more experience with adding bromine tablets to sea strainers in Southern waters, too. We're hoping to spend more time down that way next winter.

But I can report good results from putting them in the bilge. It's really cut down on the mildew "funk" smell standing salt water develops.

 

[caltexflanc]

We got better results by putting a piece of copper piping in the strainer basket.

 

[ranger58sb]

We use a copper elbow in our AC strainer, never have barnacles. Doesn't so anything for slime, though, or the occasional grass...

-Chris

 

[Seevee]

I've also had copper strips recommended to me. In the strainer. Any others?



And once a year, I flush the system with Barnacle Buster and seems to work quite well.

 

[bayview]

I used bromine tabs in the A/ C strainers because they were small. I didn't keep them in all the time just from time to time. They seemed to clear up some barnacles in a remote hose and i had no visible slime.

 

[Woodland Hills]

I’ve been using the small bromine tabs in my a/c strainers for over a year now with good results. I also drop them into the sumps and bilges whenever I remember to do it.

 

[Lucky Chucky]

I've heard about copper and have that as a backup plan to bromine tabs

 

[O C Diver]

Tried both Bromine and copper plumbing fittings and wasn't impressed. I use a dehumidifier and turn off the AC periodically. With the AC off I close the raw water seacock. The water goes foul in a couple of days, killing everything off. Guess I could speed the process up with a cap full of bleach in the strainer with the seacock closed.

Ted

 

[fryedaze]

Anyone use Bromide tablets in engine strainers?? How does it effect Zincs.

 

[Baker]

My only experience was with a neighbor that used chlorine tablets. They swore by them. ANd then in another conversation they complained about having to replace their seawater pump every year or so....when generally those things last forver! So my take away from that was chlorine eats up the sea water pump.

 

[Woodland Hills]

Engine strainers don’t need treatment since the heat kills the downstream critters. Also the engines don’t run 24/7 like an a/c strainer in the south.

Chlorine will embrittle plastics where bromine will not. Bromine in the strainers only really works to kill barnacles in the a/c units and hoses,. Unless the seawater pump shuts off for a relatively long time the bromine treated water will not make contact with the growth on the glass of the strainers. I have two pumps and strainers feeding five a/c units. the pumps run pretty much constantly in the summer as there is nearly always a thermostat calling for cold air.

 

[CaptTom]

I know the manual which came with our spa (hot tub) was very clear on using bromine instead of chlorine. Something about all the different materials in the system, apparently some of which could be damaged by the chlorine. The systems aren't all that different from what's on a boat, except the spa was not designed to live in salt water. So I figure what's good for the spa is even better for the boat.

Some chemist can chime in as to why (or why not) that's true.

 

[fryedaze]

Engine strainers don’t need treatment since the heat kills the downstream critters. Also the engines don’t run 24/7 like an a/c strainer in the south.

Chlorine will embrittle plastics where bromine will not. Bromine in the strainers only really works to kill barnacles in the a/c units and hoses,. Unless the seawater pump shuts off for a relatively long time the bromine treated water will not make contact with the growth on the glass of the strainers. I have two pumps and strainers feeding five a/c units. the pumps run pretty much constantly in the summer as there is nearly always a thermostat calling for cold air.

I would agree with engine cooler. My system runs through the trans cooler first and it doesn't get warm. I have growth problems in trans cooler and not in the engine cooler.

 

[foreverunderway]

In Charleston, SC City Marina I filled the sea strainer basket with the chlorine tabs several times a summer and it saved me having to clean the shell out of the lines in my A/C system. However, I don't believe either will keep the coils from getting coated with sediment, reducing the heat exchanging, so it was still necessary to wash out the lines with Marykate hull & deck cleaner every once in a while by recirculating it for a few minutes. I don't suppose this would be as much of a problem if the boat was in clean seawater rather than silty river water.

 

[ASLIII]

I do a retrograde flush of all my AC raw water intake ports with Salt-Away. Once monthly and keep the strainers clear- has worked well so far.

 

[Transaxial]

This may seem like an unrelated solution to clogged sea strainers, but what about using keel coolers and recirculating a non corrosive exchange fluid like anti freeze through your a/c unit. These are simple and effective , made of copper K series plumbing pipe, or a custom made unit from Fernstrum or Walter. Heat transfer should be roughly 3 horsepower or 3-4,000 btu of heat transfer per sq ft of cooler surface area in 80 deree F water. Coolers can get fouled with growth but a oversized cooler will last a long time , specially on a moving boat.

 

[stubones99]

I do a retrograde flush of all my AC raw water intake ports with Salt-Away. Once monthly and keep the strainers clear- has worked well so far.

Does anyone know what's in Salt-away? Their website has an SDS file which neglects to mention the ingredients...

 

[Woodland Hills]

In Charleston, SC City Marina I filled the sea strainer basket with the chlorine tabs several times a summer and it saved me having to clean the shell out of the lines in my A/C system. However, I don't believe either will keep the coils from getting coated with sediment, reducing the heat exchanging, so it was still necessary to wash out the lines with Marykate hull & deck cleaner every once in a while by recirculating it for a few minutes. I don't suppose this would be as much of a problem if the boat was in clean seawater rather than silty river water.

You might want to study the different effects of chlorine vs bromine on plastics. Bromine works just as well on growth without the negative effects of chlorine.

 

[Wayne]

Chlorine and Rubber

'Lo All,

First, I am not a chemist.... Ever pour chlorine into a toilet with a rubber duck-bil? If left sitting for a while, the duck-bill will be ruined because the chlorine will attack the rubber and soften it and cause it to swell, and therefor, to not seal. Same for natural rubber impellers when pumping higher-than-normal chlorine in drinking water systems. Rubber valve seats will swell and become soft, too. Most folks that I know now use nitrile impellers and valve seats (if they can find them). I once worked on a boat after the owner "shock treated" the water tanks with what I understand was 1 gallon of bleach to about a 100 gallons of water in a 200 gallon tank. He ran the treated water all through his fresh water system and then went out in the bay and made sure water was sloshed all over the insides of the tank. Shortly thereafter, the pump quit. I don't recall how long it was from the shock treatment to the pump quitting and subsequent disassembly, but when it was disassembled, the impeller was swollen, distorted and almost gooey. Some of the valve seals also had to be replaced.

 

[Alex F]

I've tried cooper strips with no luck. Within 3 weeks my A/C seastrainer was full of growth.

I'm thinking on switching to bromine tablets, if it's a reasonable solution. How often do you guys put them in the basket and how many tablets at the time?

 

[HiDHo]

I had success using a dozen copper penny’s in a/c & generator and engine sea strainer baskets on Florida Gulf coast area. It looked like because of facial wear that the coins agitated again each other maybe shredding minute particle of copper making them effective. The dock pilings showed the pea size barnacle growth.

 

[Woodland Hills]

I fill the basket with 9 tablet, the size made for hot tubs, about an inch or so in diameter. I also put one in each of the pans under my a/c air handlers to keep them draining and I toss a couple in each shower sump when I begin to smell the stale water.

 

[caltexflanc]

In summertime, in a high growth prone area, especially if there is any current at all, you have to clean the strainer on a regular basis, sometimes twice a week or more if the AC is on all the time and the boat is not cruising. Copper (which we used) or whatever is only going to help mitigate the issues, not eliminate them, particularly downstream from the strainer.

 

[Lucky Chucky]

Hi-D-Ho,

I've been putting in 3-4 tablets every 3 months and it seems to be working.

~Lucky Chucky

 

[HiDHo]

You can’t beat the cost 1 cent each. ��

 

[Alex F]

AC strainer is only part of the issue I'm dealing with.

My AC lines starting to clog up way too fast. I did a barnacle buster system flush in the fall. Then, my Salon AC line got clogged. So, I did another flushing treatment. All worked as normal. Now only 3-4 weeks later my salon and bridge lines got clogged. I don't think doing acid flush every month is practical. So, I just used the dockside water pressure to clear the clog.

I'd say that a good indication that the lines are developing growth is the green slime line on the hull just under the AC discharge. I'll be adding Bromine tablets and hope that it'll solve the problem with clogged lines and the seastrainer.