Martin C. wrote:
On Thu, 05 Apr 2012 16:43:35 -0700, Bob F wrote:

You could disconnect the wire from the pump to that thermostat above
it.

If it's as simple as disconnecting the power, and if nothing 'bad'
happens when I do so, then that's a simple plan of action.

Or, you could try remounting the pump motor

I'm realizing from this discussion that you're right. It's the
'mounting' that is probably shaking the walls which is probably
what's 'amplifying' the noise of the motor hum as it sound's louder
in the living quarters above than right in front of it.

Did I draw the direction of current correctly in these pictures?

Where pipes connects to the tank:
http://picturepush.com/public/7966064
How pipes connect to the pump:
http://picturepush.com/public/7966063

The pump should either pump hot water out of the top of the tank, through the
loop, and back to the bottom of the tank, or it "sucks" water through the loop
from the top of the tank, back through the return line and pumps it back into
the bottom of the tank. There should be an arrow on the pump body indicating the
direction of flow.

Merely turning the pump off can have the risk that legionella or other bugs may
grow in the stagnant pipes. Better to either put it on a timer, or do like I
did, and install low voltage push buttons near the sinks/showers which activate
a time delay relay to turn the pump on for a minute or so when you will be
wanting hot water. Push the button when you enter the bathroom, and the water is
hot by the time you need the sink. This, of course would involve runnung wires,
although you could do it with X10 powerline control components, or using RF
remote controls.