Air Conditioner sea strainer maintenance

We are now running one of our 16K units all week these days at the boat. The sea strainer (recently installed) is needling to have the strainer cleaned pretty much every week and I have lots of barnacles already attached to the new glass. Any suggestions to reducing the "sea life" would be greatly appreciated!


1983 Present 42 Sundeck
Twin Lehman 135's

I know several people on my dock that keep a bromide tablet in the strainer.

BlueYonder said:

I know several people on my dock that keep a bromide tablet in the strainer.

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That's what we do. We use the small one inch size. About 1/2 dozen per week. We still have to clean out the strainer every week. Here the alge bloom is really bad. The tables dissolve rather quickly. I have had the thought of only putting maybe one or two tablets In the strainer everyday to hold the alge down. Just not on the boat everyday to get that done. Don't have barnacle issues anymore since we started using the tablets however.

Barnacles were so bad in the past I had to change some of hoses. Found those suckers as far away as 15' up the longest hose on the aft AC. Was a little shocked to see that.

Try using a toilet brush to scrub out the glass. You may find that the ones on there might come off rather easily on that slicker surface.

Try putting a piece of copper pipe in the strainer. Or some copper pennies.

and don't tell EPA

stubones99 said:

and don't tell EPA

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They are not big on tin. I think copper is OK at least for now.

The key to good air cond is the intake strainer.

The best are the "Y" type mounted directly on the sea cock.

At O' dark 30 its one hand easy to check the strainer , or push a broom stick out the sea cock to get rid of the Jelleys.

Necessary as many times the sea cock gets plugged , bot the strainer.

Just wondering if anybody has installed a keel cooler for their intakes?
I know commercial boats (mostly steel and aluminum hulls) use them but could one be constructed out of fiberglass? Maybe a half pipe glued to the hull with intakes on each end? If so that should solve these problems?
Maybe a project on the next haul-out?

We use the copper pipe method; pennies are not as good as they are really zinc. I got in the habit of taking a toilet brush and using it to clean the inside of the glass a bit whenever I cleaned the strainer. We were once in a marina with a lot of warm water current, so it was growth city if not maintained.

Fresh water looks better every time I read a thread like this. I clean my strainers once a year when I winterize all the systems, at that time not having to winterize looks pretty sweet and the problems that come with saltwater disappear.


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I want to thank the OP (Forklift) for starting this thread. It reminded me that I haven't cleaned my strainer since I bought the boat a couple months ago. So, went below, found the proper strainer and cleaned out the 1/4 inch of algae totally covering it. Also found and cleaned the engine raw water intake strainers and did them. I'm still new enough that I need to be reminded of the general maintenance procedures required on a live-aboard. Again, THANKS!

When you run the a/c all the time the sea life love it. They love the water flow and places to hold on to. Here in the keys I use a Cloirine pool tablet in the strainer after cleaning it each month. Since I've done this the growth it less but still have to check for grass in the strainer when I notice a drop in water discharge. Every 6 months I flush the system with a heat exchanger acid wash ,and back flush the system. Works for me, just my $.02

Thanks for all the informative responses!


1983 Present 42 Sundeck
Twin Lehman 135's

We are using several Bromide tablets and a piece of copper pipe

the copper pipe I sand a little each Friday when I clean the strainer as long as I do this I never get barnacles only a little grassish growth

but if I am traveling and miss a week then I start to see some barnacle growth

For plastic boats a keel cooler is OTS.

Air cond , noisemaker or main engine , OTS.

Google keel coolers.

I'm thinking copper pipe, wire and pennies are an old wise tale. Is there enough contact time with the 500 to 1000 gph running over the copper to really be effectice as a toxin to barnacles or growth? Houses have had copper pipes for years with 100's of feet installed and yet the water isn't toxic to us and the barancles will live in a more toxic arena than we can. If it works for you great but personally, I'm not sure. I think regularly cleaning and bromide tablets will be the most effective.

I stacked up bromide tabs and the chemical jammed my threads. When I finally got the bronze cap off I Never Seized the threads. I also have copper tubing in the bowl.

Larry M said:

I'm thinking copper pipe, wire and pennies are an old wise tale. Is there enough contact time with the 500 to 1000 gph running over the copper to really be effectice as a toxin to barnacles or growth? Houses have had copper pipes for years with 100's of feet installed and yet the water isn't toxic to us and the barancles will live in more toxic arena than we can. If it works for you great but personally, I'm not sure. I think regularly cleaning and bromide tablets will be the most effective.

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Agree on the copper but when I sand the pipe each week it seems to help but it may be my imagination

Deckape said:

I use a Cloirine pool tablet in the strainer after cleaning it each month.

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I would check on the use of Chlorine... IIRC, this can cause all sorts of metal deterioration in a saltwater environment. Isn't it an oxidizer? I don't know the science, but I remember someone saying it the difference between chlorine and bromine was significant.

No, not a tale at all. A few pennies in a salt water aquarium can kill all the crustaceans, including barnacles, shrimp, crabs, etc... That's why they say take off all jewelry when servicing a salt water tank.

So, it turns out that copper will kill them since their blood has copper and the combination of more copper to a balanced copper based blood circulation system is fatal.

It won't affect any plant growth though.

Copper used to be used for ships hulls to stop borers and tubeworms from eating the oakum and caulk from the joints as well as eating holes in the wood hulls. We used to use cuprous oxide (copper oxide) in anti-fouling paints, but found that the leaching of copper from the paint killed the marine life many fishermen (in the same boats) were fishing for, so they banned all biocides from hull paint in the late 1980's.

All I can say Larry is that I easily noticed a difference after I went with the copper pipe.

Copper is in bottom paint after all.

copper based paints are banned in WA state and a few others...

stubones99 said:

copper based paints are banned in WA state and a few others...

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But what about copper pipe?

Capt.Bill11 said:

But what about copper pipe?

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Seriously, how could copper pipe be banned or policed? "Hey Joe, call the underwater EPA. Methinks Harry has copper pipe or pennies in his sea strainers."

How about this....heard it. Round Up added to the bottom paint to handle the plant growth???

Have to lend a bit of support to Larry in that stuff may not grow on the pipe..but the whole system?


Saying bottom paint has copper in it as a comparison...well wouldn't that be like saying my bottom paint will keep the stuff from growing on the dock/pilings? Which it doesn't....heck it doesn't stop it 1 inch away on the rudder, etc.


And bottom paint is designed to leach...I don't think copper pipe and pennies are.


But unlike some around here...just because it's hard for me to believe it is that effective...I would take many on heres word for it and give it a try...what can it hurt?


Chlorine and bromine tablets I might shy away from...but simple copper that I drink out of it...can't hurt to do my own experiment.

"How does copper get into my drinking water?
The major sources of copper in drinking water are corrosion of household plumbing systems; and erosion of natural deposits. Copper enters the water (“leaches”) through contact with the plumbing. Copper leaches into water through corrosion – a dissolving or wearing away of metal caused by a chemical reaction between water and your plumbing. Copper can leach into water primarily from pipes, but fixtures and faucets (brass), and fittings can also be a source. The amount of copper in your water also depends on the types and amounts of minerals in the water, how long the water stays in the pipes, the amount of wear in the pipes, the water’s acidity and its temperature."

If you recall my post, I said it messed up invertebrates which people are not. It messes up shell fish, and is a required trace element in our bodies.

They banned it as part of bottom paints. The IMO treaties require no Biocides be added to a bottom paint since it kills what attaches to a bottom and tends to leach out into the water around the boat(s).

"They banned it as part of bottom paints."

When I read many cans of bottom paint the copper content is still listed. 30% +

Did someone forget to inform the bottom paint mfg folks?