I work as a water engineer
for a Canadian municipality. I believe in chlorination.
I use a test kit (Hach or Taylor in North America) and calcium hypochlorite (65% free chlorine). For 200 Litres, I would use ~1/2 teaspoon. You could also use sodium hypochlorite, but if so, I would suggest J-12 ( sodium hypochlorite - 12%free chlorine) as opposed to household bleach. I aim for a free chlorine residual in my tanks of 0.3 to 0.8 mg/L (ppm) at all times. I woudn't get upset if the residual was 0.1-1.5, as long as it is reasonably palatable. This will keep the water sweet and maintain already clean pipes clean. It will also give your towels and face cloths a fighting chance against bad odours. When the residual falls or disappears, mix a little more chlorine back in.
Sources that can supply groundwater should be favoured, as there are typically lower concentrations of organics, ammonias, and nitrogen species. These are the things that create the bleach-like taste and odour. Really - adding chlorine to pure water creates no odour or taste.
Surface water is fine as well; and if it doesn't react so badly with the chlorine that you can't handle the taste, it is fine to drink from the tanks.
These residuals will maintain a guard against algae, sulfur reducers, and other pests. As for killing the pathogens: most will be gone within seconds. But for some viruses and most protozoans (amoebic dysentery, giardia lamblia and cryptosporidium), it may be best to wait overnight for them to be knocked inert at 0.5 mg/L. They hibernate in a cyst-like state. At very few docks should you have to worry about these, however.
Bottled water? Still the best for making tea and coffee, but not necessary for drinking if you maintain a free chlorine residual.
However, if you have sediment in your tank and green gunge in your pipes, it will be tough for these low residuals to come out on top. Remove the sediment and treat the pipes to a much stronger dosage for a bit. Got the sediment out but afraid to give the pipes a strong dose? Use the water at 2-5 ppm for a tankful for showering, cleaning
, and cooking
; and drink the bottled water til the next time.
The filter on the filler hose is a great idea, EC - one in which I am going to invest. I have bits of coral
in my tanks, thanks somehow to the previous owner and have a filter on the exit now. An entrance filter would have stopped that problem.