[Greenbuilding] [BULK] Hot Water Return Revisited WAS Windows

[njh]

On Thu, 19 Feb 2009, Lawrence Lile wrote:

> 3. There is another type of hot water return system that uses a small 
> pump at each load.  You pump the hot water line into the cold water line 
> through a one-way valve.  The pump is limited by a thermostat.  The user 
> presses a button to get hot water.  This recycles the water that the 
> user would have wasted down the drain, waiting for hot water, and so you 
> could argue it is more efficient than a stock plumbing system.  At over 
> $100 a whack, it is only for special situations (long pipes to the 
> kitchen, for instance) or money-is-no-object green homes.

You don't need a pump, merely a pressure differential.  You could do this 
using a thermostatic valve, a pressure reducing valve, two check valves 
and a pressure vessel.  (A clever person could make all of these in a 
single HDPE unit)

Hot tap turns on, water flows from hot tank to cold pressure vessel, water 
warms up, thermostatic valve opens and out comes water.

Cold tap turns on, water flows out from pressure vessel until below 
pressure reducing valve pressure, flows from mains.  The cold water could 
be dumped into a non picky load such as toilet cistern.

njh