On Tuesday, October 20, 2015 at 12:09:11 PM UTC-10, Dave Smith wrote:
> On 2015-10-20 6:06 PM, dsi1 wrote:
>
> >> When the water has been in the pipes for a while the heat radiates
> >> and the water cools. When you turn on the hot water tap at the end
> >> of the pipe only cold water passes through it until the line has
> >> been purged of cold and the hot water is coming through. If the
> >> pipes are a wider diameter there will be a lot more volume of now
> >> cold water that has to be purged through the pipes before the hot
> >> starts to come out.
> >
> > The long metal pipe also acts as an efficient heat exchanger.
>
> Actually, in this situation that would be inefficient, not efficient.
>

I have no idea what you mean. Aren't most heat exchangers fluids moving through skinny pipes? Isn't that how radiators and solar water heaters work?

>
>
>
> > Hot
> > water going into one end would come out cold on the other. It's a
> > pretty cool effect - no pun intended.
> >
> Sorry, but I had to look way to hard for the pun.