T&T: Chlorine tablets & jelly fish

[Milt Baker]

I've been using swimming pool chlorine tables (broken into smaller chunks) in the air conditioning sea strainers aboard my Nordhavn and, before that, my Grand Banks for perhaps a decade.  When the seawater temperature is greater than about 70 deg. F and I'm using the conditioning a lot, I usually add one chunk per strainer per week and I'm sure to let the pumps run for at least 30 minutes after adding the chlorine to get a good stream of the chemical into the lines to kill any growth that may be trying to reside there.  Although the pieces of chlorine dissolve after a few hours of running or a day or two of sitting idle, this seems to keep the air conditioning lines clear of hard fouling and we have never been troubled with plugged lines or poor raw water flow.  Only downside I've noted is that with some Groco sea strainers the sight glasses turn a bit cloudy.

Answers to your questions:

--Yes it works.
--I have noted no effect on stainless steel, monel or plastic strainer baskets.  I like the plastic ones because, unlike the metals ones, they seem to last forever.

--Milt Baker, Nordhavb 47 Bluewater, Korcula, Croatia    


Jim wrote: 

In cleaning the nettles/jelly fish from the AC raw water filters,
I noticed that a few small barnacles growing inside the strainer bowl.
Several boats here use chlorine tablets in the baskets to stop the growth.
Questions:
Does this work?
Will the chlorine tablets cause any damage to the SS basket?
How many tablets?
How long will they last?