Bleach Tablets

[LEOCAT66]

Have been speaking to a fellow sailor in the next slip about growth in the salt water intake for the engine (YANMAR 3 GM30 F). He advised that he has been using bleach tablets in his Groco strainer for a while. Since the tablets are slow to dissolve they provide extended protection and he sees a much cleaner strainer in general and assumes that the cleaning and or protection, extends to the elbow, etc.

Anyone tried this method or have reason to reject it due to potential damage to the system?

[Cheechako]

Not sure, but if any components in the system are aluminum it may not be good. I doubt it will help with the exhaust elbow, coking is the probably there not bio growth.
Frankly I wouldn't do it as a clean strainer is not a big problem unless you get eel grass etc in there and bleach wont help that.

[pesarsten]

Using bleach tablets , which I would presume are Chlorine tabs for use in a spa or pool, is assuradly a very poor idea. The oxidizer nature will cause severe damage to any metal that oxidizes. In addition, the storage and handling can be pretty dangerous. Read the label! Tabs can ignite solely from becoming wet or damp and can explode from impact ( as in when hammered to crush them) .

All in all, not really " boat friendly " stuff.

[LEOCAT66]

Thanks for the response. I was aware that bleach tablets might be a poor idea for metal and or rubber surfaces.

Never having had them I was not aware that there was a warning label associated with them. Seems odd though that they are used in hot tubs and the like where they certainly come into contact with water continually.

Back many years ago we had a hot tub and part of the maint. included the use bromine tablets in the system to keep growth down in the pump etc.

[MarkJ]

Bleach is fine on rubber.
But the water that comes in the raw water inlet then circulates through the metal, to wit, aluminium heat exchanger. That would not be good.

[LEOCAT66]

Thank you Mark, always was advised not to put it in the head bowl so figured it was a rubber issue. Won't be using it in either place.&

[sailjumanji]

We used Bromine tablets in our strainer for raw water pickup for the air conditioner. Used chlorine tablets for a while, but someone advised that bromine was less corrosive. It did manage to keep the green algae from accumulating, but it made the Groco plastic bowl opaque to the point that you could not see the screen. Plus I had a talk with Dometic - maker of the AC unit - and they said they did not recommend using the tablets with their cooling coils. I stopped. And purchased a replacement bowl for the water strainer.

[thinwater]

Originally Posted by MarkJ

Bleach is fine on rubber.

Actually, not true. Chlorine is the leading cause of water closet parts failures and regular use has been proven to increase permeation in holding tank hoses. While there are some elastomers that do very well with bleach, most are slowly affected.

Bleach really makes sense only in non-aluminum freshwater tanks. Any other boat use should be approached circumspectly. It is a very aggressive chemical that affects many materials, given enough time.

[MarkJ]

Originally Posted by thinwater

Actually, not true. Chlorine is the leading cause of water closet parts failures and regular use has been proven to increase permeation in holding tank hoses. While there are some elastomers that do very well with bleach, most are slowly affected.

I'm sorry, but its just not possible for me to ever be wrong.... A while ago I soaked a Jabsco O ring in bleach for a week then used it in the head for a year.


Chlorox and Mark A boat filled love affair.

[Nicholson58]

Originally Posted by LEOCAT66

Thanks for the response. I was aware that bleach tablets might be a poor idea for metal and or rubber surfaces.

Never having had them I was not aware that there was a warning label associated with them. Seems odd though that they are used in hot tubs and the like where they certainly come into contact with water continually.

Back many years ago we had a hot tub and part of the maint. included the use bromine tablets in the system to keep growth down in the pump etc.

I maintain our pool & spa. I don't know about sea water but in a pool - The tablets are slow to dissolve. If the Ph of the water & dissolved tablets yields lower than 7 it is likely to attack the metal parts, especially aluminum. It might remove calcium deposits in your heat exchanger. If the Ph is high, you may get unwanted mineral deposits. For killing the critters, I put about 3 cups of straight bleach in the strainer; wait a few minutes; pump it into the engine; wait 5 - 10 minutes; start the engine and go. The blackest crud comes flying out the exhaust. Pretty well takes care of the zebra mussels & algae here on the Great Lakes.

[txh2oskier]

We're in St Petersburg Florida at the moment and you wouldn't believe the barnacles that have accumulated in the a/c and refrigerator strainers. Does anyone have any suggestions for slowing them down? How about a bit of copper in the strainer?

Brian

[hellosailor]

A friend of mine uses "bromine" chemicals in a hot tub system, and I still found a pair of cotton shorts had gotten punked out by the chemistry. Apparently it is safer than chlorine but still not "safe" for everything.


O-rings and other "rubber" parts may be any of hundreds of compounds. Viton, rubber, all kinds of elastomers that all just look like "rubber" to us non-chemists. So anecdotal tales of "it wasn't harmed" without a way to know exactly what it was made of...Sorry Mark, all you've proved is that chlorine doesn't change the black color of o-rings.(G)
But for fun you can put a few drops in a bottle of cola, and watch it turn into 7-up. Or so it seems.(G)


I think the bromine pill in the water intake would be very attractive IF you could be certain of everything that it touched, and certain that it would do no harm. I'd considered throwing chlorine (tablets or a leaky bottle) into a "diaper" under the boat to help the bottom paint, but then again, chlorine could also attack the bottom paint, gelcoat, stainless rudder stock...Who knows? None of that is intended or tested for continual use in a highly chlorinated environment, is it? Same for bromine.
Maybe the trick would be to put a UV-C lamp, designed to sterilize, inline in the intake. Kill 'em that way.

[a64pilot]

Originally Posted by txh2oskier

How about a bit of copper in the strainer?

Brian

I've wondered that myself, but unless mistaken I think critters will grow just fine on copper sheeting, wasn't copper sheeting used sometimes on wooden boats to keep the worms from burying in?

[Jim Cate]

IIRC, it only takes something like 10-25 ppm of free chlorine to be rapidly lethal to most organisms in water. At those concentrations, disastrous reactions with your engine components seem unlikely. If the application envisioned is for longish periods of idleness, even lower concentrations will be effective biocides and surely not harmful to rubber, cast iron, stainless and the other components of your cooling system.

Jim

[hellosailor]

Jim-
I'd suspect the "pool tablets", typically the size of a hockey puck or roll of electrical tape, are designed to release that concentration of chlorine into a swimming pool. Even a small swimming pool is going to be HUGE compared to most cooling systems on sailboats, so...perhaps in the intake strainer it becomes 1,000ppm? or 100,000ppm?


"A simple exercise left to the reader" as they used to say. Calculate the volume of your cooling system, the diffusion rate from your strainer, and compare to the instructions on the pool tablets.(G)


There may very well be a pony in this pile.