Originally Posted by Airtandem
I have city water that has been treated with chlorine, isn't that good enough to sanitize the lines? I usually fill with our city water before traveling.
City water that is treated with chlorine must
have a concentration low enough to still be drinkable, meaning less than 4 parts per million. That's enough to make sure no microorganisms can live in the water between the water treatment plant and your faucet, but only because ALL of the water is treated ALL of the time.
In your Airstream— or any other RV— you're not
adding chlorine all the time. The chlorine that's in the city water you used to fill your tank will evaporate in 24 hours or less because you're not constantly adding more to replace what evaporates. And when all the chlorine is gone from the water, harmful microorganisms can grow. So you periodically shock-treat the freshwater system by adding a much larger dose of chlorine, more than is safe to drink, to make sure that whatever might be adhering to the tank walls, pipes, valves, etc. is well and truly dead. Then you flush out the chlorinated water to get rid of the non-drinkable water and the dead microorganisms.