Water Heater Expansion Tank
 

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

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

On 5 May 2005 08:06:12 -0700, someone wrote:


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

Theory over practice.

If the check valve was a distance approaching inifinity away, being
that the total volume of expansion is finite (and rather small), and
there being some (very small) elasticity in the pipes, tank, valves,
water itself, you COULD be far enough away that the now small rise in
pressure (from a very small volume being added to a very large one)
would not be enough to force the valve open.

Has practice shown that 150 feet is enough?

Try it and see. If his T&P keeps dribbling, he could still put the
tank in. But he may find he doesn't need to.


Reply to NG only - this e.mail address goes to a kill file.

On Thu, 5 May 2005 09:28:48 -0400, "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?



I don't know about 150 ft, I do know about 135 feet; I needed an
expansion tank.
rac