Originally Posted by
DJW
Next time the ageing barrel is empty, add a teaspoon of epsom salt before you fill up the barrel. If it stops the cloudiness, you could try less and less to see how little it takes. I don't know if it will work, but it would be interesting to find out.
Epsom salt has magnesium in it, and magnesium interferes with the crystallization of calcium carbonate. The cloudiness is probably tiny crystals of CaCO3 that form as the water warms up. After a few hours in the tank it dissolves again.