Speedy Jim wrote:
default wrote:


Heat traps are small ball check valves. They prevent hot water
"migration" (small circulating flow) out the Cold and Hot supplies
when no water is being drawn. It is a small energy-saver/.



Why do you need a ball valve? Wouldn't a simple U bend do
the trick?

I don't see how it would....Unless they were quite tall and very well
insulated.

Those "heat traps" use lightly loaded check valves to counteract the
small pressure differential caused by the difference in specific gravity
of hot and cold water. What they do is keep the hot water from moving up
and out of the water heater and into the piping and cold water "sinking
down" into the tank from those same pipes during idle periods.

When a hot water faucet is opened, mains pressure easily pushes those
valves open and flow proceeds normally.

Hydronic heating systems sometimes have similar valves to prevent a
similar kind of thermosyphon flow from keeping the heat in the boiler
from reaching the baseboard units when the circulator pump isn't
running, since water will still flow through a stopped centrifugal pump.
They used to be called "gravity valves", and may still be.

Jeff




These are actually easier to install:
http://www.perfectioncorp.com/water/heattrap.html
since they go straight in-line from the heater threaded bosses.

Jim


--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"As long as there are final exams, there will be prayer in public
schools"