Tea? Forget tea, good strong coffee, need that caffeine kick.
Just kidding, I know how you Brits are with your tea, same as us with coffee. I do have a couple of tea pots, the hot water heater doesn't crank out good boiling water that would make a decent cup of tea.
I think a lot of it has to do with your water heating system. As mentioned, plenty of water heaters here are glass lined. I've noticed that milkiness you mentioned, but it seems to dissipate after a little bit, which leads me to believe that some gas is gassing out.
I've tried a 25% water change on a 55 with straight cold in the winter, the tank went from the mid 80's to the low 70's. Talk about some sluggish angels, they moped around until the water warmed up.
I wouldn't think of doing this in a juvie tank, they get 50% to 80% water changes. I'm sure that large of a drop would not be good.
Another thing I've been doing with some 40 gallon tanks is adding water then adding dechlor after they are filled. These tanks are used, with overflows. I turn off the sponges I use for bio filtration, run water in until a 40 gallon can is half full from the overflow, then add dechlor. I've been doing this with everything from dime size juvies to some adult wilds, and have yet to have a problem.