In article .com,
writes:
I have noticed that when running hot water using a combi, at a reduced
water rate, the water is "very" cloudy. It clears to very clear in a
glass in about a minute. Yet, when the flow is faster the water is
always clear. Does anyone know why this happens?

It's dissolved air which has come out of solution.
It's caused by sudden pressure drop and/or temperature rise.
With slow flow and high temperature, both these effects are
maximised.

--
Andrew Gabriel