I hear you, but anything over 50ppm free chorine is not recommended even for relatively short term contact with copper. 1/2 cup of bleach in a gallon is about 1,250ppm free chlorine. I don't worry about the pumps. Contact there, if any, is really short. The grounding strap is where I see the real problem soaking for an hour at a time every two months.
It is certainly not as bad as dropping calcium hypochlorite tablets in and leaving them for long term (Ouch!), but is it still shortening the life of the copper grounding strap un-necessarily. We can argue forever if the corrosion rate is enough to make a real world difference, but since bleach is not really needed, in my thinking, it is better avoided.
I am betting chlorine bleach is one of the reasons so many people have problems with the copper fittings in their holding tanks corroding, since adding bleach is a common (and bad!) recommendation there as well. I had the hoses off one of my tanks today, and after 20 years of full time liveaboard service, the copper looks like new. So we know that it is not the normal "stuff" in the holding tank that corrodes other boat's copper fittings...
---In amelyachtowners@..., <yahoogroups@...> wrote :
You are correct, however some of the recommendations in this thread were much higher than I gave which was 1/2 cup to a gallon of water for 1 hour, then use a wet vac to suck it out...then add 8 liters of fresh water. Additionally, if they follow my method, the "bleach" never reaches the pumps.
It is a common recommendation in Europe to place a spa chlorine tablet in the bilge and the sea chest. I know because I have been told by some Europeans, and because I have read this on the French Amel Owners Group. Unfortunately, this is really bad advice and ruins lots of things. I saw more copper saltwater manifolds fail on European owned Amels than others. I assume it is because of this misinformation.
Again, you are correct, Bill, too much is really bad.