Could someone explain why the sound of water pipes changes with the incoming waters temperature ??? Its not like there`s a change of friction going on… 
The hot water causes the pipes to expand. The new size makes them sound different.
The same question answered.
I never put hot water in my water pipe.
Actually, it never got a decent answer.
I still believe that the viscosity has a large impact on the pitch of the sound, but I haven’t been able to prove it.
Maybe a question for the Master?
Yeah it got answered - viscosity is not a factor.
It’s pretty clear that the viscosity is not a factor for the propagation of sound.
I believe, however, that the sound arises when uneven edges and depositions along the surfaces cause eddy currents and turbulence in the flow, and to me it’s equally obvious that this would depend on the viscosity of the liquid.
One reason I’m arguing so strongly in favour for the viscosity is that it’s the parameter that changes the most over the temperature spectrum we’re looking at. (cite)
But if you can come up with a more plausible explanation for the origin of the noise, I’m all ears.