racarson wrote:
I just put a back flow preventer on my water meter.

The meter is in a pit outside the house. I would estimate the
meter/back
flow preventer is 150 ft away from the water heater in the basement.

I have been told that due to the distance between the meter/back flow
preventer and the water heater that I do not need to put an expansion
tank
on the water heater.

Does anyone have experience with back flow preventers located 150 ft
from
the water heater? Is it necessary to install an expansion tank in
such a
situation?

Thanks,
rac

A back flow preventer keeps -any- water from moving back into the
system. You therefore have a totally sealed system until you open a
faucet somewhere. Water heaters cause the water to expand thus raising
pressure. Raise it far enough and the TPR valve opens. It doesn't
matter if the backflow preventer is 1ft or 1 mile away, the pressure
will still rise.

Harry K