Ugly Raw Water Blockages - A Fouling Story

We're spending quite a bit of time in marinas these last few months, as I'm doing some contract work and Admiral Ley needs a safe home while I'm away from the boat.  

This means that our sea water cooled refrigeration and airconditioning systems are running frequently in estuarine waters with a very high fouling capability.

Coming from a relatively cold water background (Melbourne, Australia) I'm still amazed at how quickly an anchor, or chain, or in this case a raw water inlet, can become completely fouled by marine growth in these warm water areas.  The image at right shows the problem - the hose tail at left is almost closed with barnacles, and the hose tail at right has a decent oyster growing - just what we don't want.  

 
When we look at the hose, the situation is obviously worse. Large clusters of barnacles and yet another oyster are almost completely blocking the inlet hose.  Note this is 1.5" (40mm) hose, that feeds a manifold with multiple outlets for refrigeration, air conditioning, deck wash, genset etc.

To counter the problem we now place a chlorine tablet in our raw water strainer every other day, when we're in a marina.  We use standard swimming pool chlorine tablets, that dissolve in just a few minutes after placement.  These do a great job of stopping the growth from the strainer basket onwards.

Special Note :  You MUST NOT use chlorine tablets on a seawater inlet that feeds your R.O. water maker - it will destroy the membrane(s) !

Chlorine tablets also clean up the hoses really well,  but they can't help with the hose and fittings that are in the line before the strainer.  So now we replace that hose every twelve months - a half day boat project that keeps the systems running and my back and shoulders in fine trim (its a b**g*r to get at), and my knuckles suitably skinned.  Boat jobs.

Along the west  Malaysian coast, from Singapore to Langkawi and northwards into Thailand, this type of fouling is all to common.  In Kuah Harbour (Langkawi), the long term cruisers know that you must lift your anchor chain by 4 or 5 meters one day, and then lower it back again the next day, in a never ending alternating sequence, to stop the aggressive growth there from fouling the chain that is between the water surface and the muddy bottom.  This really does work, though nothing will stop the change to the chain galvanising caused by the very special mud in Langkawi.  But that's another story.....