Question:
I went down to the boat last night and put 27 ozs ofclorox into the fresh water tank and then added 75 gallons of water. Iwaited approx 30 minutes and ran all of the water out of the tank andrefilled with fresh water.

Answer: The only way to be sure that your fresh water tank is safe to drink, is toclean it out and start fresh with filtered and monitored water. You can findtorpedo style "in-line" water filters that you can splice into a fill-hose,and you can ask for safe water sources when you re-fill. But first: Dump a gallon of chlorine bleach into your potable tanks. Turn on allthe taps and shower to get this bleachy water into all parts of your syatem.Turn off the taps, leaving the solution in the system overnight. The nextday, drain the system through the taps, fill the tanks 1/2 way with knownsafe water, and drain again. Repeat last step.Now you are ready for a safe water experience. Good drinking! Note:Sometimes whole houses need this fix- homes like farms with wells andlivestock can sometimes get "systemic infections" from transientrain/erosion-borne bugs like e-coli. That is how I learned to do this. Itworks! On a boat it can improve the flavor of the water a lot, especially ifyou spring for a fill-filter

I suppose it would be a drag to do the job by hand, but any campingstore carries hand purifiers, the best made by MSR, which will makesewage safe to drink. The purifier by MSR costs about $65, and we whobackpack all carry one [or equivalent]. Another option [depending onwhere you are] is to pump out all of the water, and get new from areliable source, after cleaning the tanks.