On Thu, 6 Aug 2009 13:06:41 -0500, "Ralph Mowery"
wrote:


"Phisherman" wrote in message
.. .
I plan to purchase a tankless water heater to replace a failing water
tank. The current vent is a 6" diameter vent pipe. I need a 7.4 GPM
unit (4 bathroom house with 3 showers) and considering a Rheem
GT199PVN. I noticed some tankless heaters have two separate vent
pipes (one intake and the other exhaust). Some have one vent pipe
with one pipe inside the other. If I choose the later I will need an
additional hole in the side of the house (no chimney). What are the
pros and cons of two separate pipes than just one pipe with an
interior pipe? Are two separate pipes functionally better than one
pipe inside the other? I'm a bit concerned when I need to replace the
new heater (hopefully in 10+ years) that I may have to deal with
patching or resizing holes. I've seen so many different kinds and
configurations in water heaters and vents. Unemployed right now, I
don't have $1600 to spend on installation, I got the time to do it
myself. Any tips on installation are appreciated.

While you are at it , does the gas supply have enough capacity to run the
water heater ?
I still think it is cheaper to just run the old style tank in the long run.



I'm in e.TN. Two adults in the house. The cold water is warm enough
to shower without being heated, although somewhat uncomfortable. An
old-style tank is about $990 (Rheem direct vent), and a tankless about
$1400 (or $1200 if I order online).