T&T: Fresh water Tank problem

[Robert Kassal]

Rich wrote
'Every time we get on the topic of f/w system cleaning, I read the comment
about how fast chlorine dissipates from the tank water.  However, the vents
on my 120-gallon tanks consist of 1/4-inch copper tubing.  Does anybody
really think all the chlorine in a fresh fill of 120 gallons of city water
is going to get out of solution that fast, especially if the tank remains
full?'

Rich, I think folks are confusing dissipating and reacting. The chlorine is
added so that it can react with biological contaminants and destroy them. It
does the same thing to plastic and rubber parts too and probably also reacts
with aluminum. So, yes the level can go down with long storage.

In six years of essentially full time cruising and living aboard including
lots of time spent in Florida, I never had a need to shock a water system, nor
did I ever add extra chlorine and I never had a tank go 'bad'. Simply use the
water from the tank, not a hose as others have said.

If you do have a need to shock a tank that has been neglected, remember 10ppm
Cl is enough. If you want to do a maintenance dose when filling with untreated
well water, 0.1-0.2 ppm ought to be enough.

Another poster asked about the newer chloramine treatment. You cannot buy
anything to add to the tank to provide this (known as combined chlorine).
Water companies use it to treat surface water (lakes and rivers) which contain
organics like algae. The chloramine reacts differently than chlorine and does
not produce carcinogenic haloforms.

Bob